datetime — 基本日期和时间类型 ¶

感知和单纯对象 ¶

Date and time objects may be categorized as “aware” or “naive” depending on whether or not they include timezone information.

With sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, an aware object can locate itself relative to other aware objects. An aware object represents a specific moment in time that is not open to interpretation. 1

A naive object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality.

For applications requiring aware objects, datetime and time objects have an optional time zone information attribute, tzinfo , that can be set to an instance of a subclass of the abstract tzinfo class. These tzinfo objects capture information about the offset from UTC time, the time zone name, and whether daylight saving time is in effect.

Only one concrete tzinfo 类， timezone class, is supplied by the datetime 模块。 timezone class can represent simple timezones with fixed offsets from UTC, such as UTC itself or North American EST and EDT timezones. Supporting timezones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC.

常量 ¶

datetime 模块导出下列常量：

datetime. MINYEAR ¶

最小允许年数在 date or datetime 对象。 MINYEAR is 1 .

datetime. MAXYEAR ¶

最大允许年数在 date or datetime 对象。 MAXYEAR is 9999 .

可用类型 ¶

class datetime. date

理想化单纯日期，假定当前公历始终且永远有效。属性： year , month ，和 day .

class datetime. time

An idealized time, independent of any particular day, assuming that every day has exactly 24*60*60 seconds. (There is no notion of “leap seconds” here.) Attributes: hour , minute , second , microsecond ，和 tzinfo .

class datetime. datetime

A combination of a date and a time. Attributes: year , month , day , hour , minute , second , microsecond ，和 tzinfo .

class datetime. timedelta

A duration expressing the difference between two date , time ，或 datetime instances to microsecond resolution.

class datetime. tzinfo

An abstract base class for time zone information objects. These are used by the datetime and time classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).

class datetime. timezone

A class that implements the tzinfo abstract base class as a fixed offset from the UTC.

3.2 版新增。

这些类型的对象是不可变的。

子类关系：

object
    timedelta
    tzinfo
        timezone
    time
    date
        datetime
								

timedelta 对象 ¶

A timedelta object represents a duration, the difference between two dates or times.

class datetime. timedelta ( days=0 , seconds=0 , microseconds=0 , milliseconds=0 , minutes=0 , hours=0 , weeks=0 ) ¶

所有自变量是可选的且默认为 0 . Arguments may be integers or floats, and may be positive or negative.

Only days , seconds and microseconds are stored internally. Arguments are converted to those units:

• 一毫秒转换为 1000 微秒。

• 一分钟转换为 60 秒。

• 一小时转换为 3600 秒。

• 一星期转换为 7 天。

and days, seconds and microseconds are then normalized so that the representation is unique, with

• 0 <= microseconds < 1000000

• 0 <= seconds < 3600*24 (一天的秒数)

• -999999999 <= days <= 999999999

The following example illustrates how any arguments besides days , seconds and microseconds are “merged” and normalized into those three resulting attributes:

>>> from datetime import timedelta
>>> delta = timedelta(
...     days=50,
...     seconds=27,
...     microseconds=10,
...     milliseconds=29000,
...     minutes=5,
...     hours=8,
...     weeks=2
... )
>>> # Only days, seconds, and microseconds remain
>>> delta
datetime.timedelta(days=64, seconds=29156, microseconds=10)
										

If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round-half-to-even tiebreaker. If no argument is a float, the conversion and normalization processes are exact (no information is lost).

If the normalized value of days lies outside the indicated range, OverflowError 被引发。

Note that normalization of negative values may be surprising at first. For example:

>>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)
										

类属性：

timedelta. min ¶

The most negative timedelta 对象， timedelta(-999999999) .

timedelta. max ¶

The most positive timedelta 对象， timedelta(days=999999999, hours=23, minutes=59, seconds=59, microseconds=999999) .

timedelta. resolution ¶

The smallest possible difference between non-equal timedelta objects, timedelta(microseconds=1) .

Note that, because of normalization, timedelta.max > -timedelta.min . -timedelta.max is not representable as a timedelta 对象。

实例属性 (只读)：

支持的操作：

注意事项：

1. This is exact but may overflow.

2. This is exact and cannot overflow.

3. Division by 0 raises ZeroDivisionError .

4. - timedelta.max is not representable as a timedelta 对象。

5. String representations of timedelta objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example:

   >>> timedelta(hours=-5)
   datetime.timedelta(days=-1, seconds=68400)
   >>> print(_)
   -1 day, 19:00:00
   										

6. 表达式 t2 - t3 will always be equal to the expression t2 + (-t3) except when t3 is equal to timedelta.max ; in that case the former will produce a result while the latter will overflow.

In addition to the operations listed above, timedelta objects support certain additions and subtractions with date and datetime objects (see below).

Comparisons of timedelta objects are supported, with some caveats.

The comparisons == or != always return a bool , no matter the type of the compared object:

>>> from datetime import timedelta
>>> delta1 = timedelta(seconds=57)
>>> delta2 = timedelta(hours=25, seconds=2)
>>> delta2 != delta1
True
>>> delta2 == 5
False
								

For all other comparisons (such as < and > ), when a timedelta object is compared to an object of a different type, TypeError is raised:

>>> delta2 > delta1
True
>>> delta2 > 5
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'datetime.timedelta' and 'int'
								

In Boolean contexts, a timedelta object is considered to be true if and only if it isn’t equal to timedelta(0) .

实例方法：

timedelta. total_seconds ( ) ¶

Return the total number of seconds contained in the duration. Equivalent to td / timedelta(seconds=1) . For interval units other than seconds, use the division form directly (e.g. td / timedelta(microseconds=1) ).

Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy.

3.2 版新增。

>>> # Components of another_year add up to exactly 365 days
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
...                          minutes=50, seconds=600)
>>> year == another_year
True
>>> year.total_seconds()
31536000.0
									

>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> ten_years = 10 * year
>>> ten_years
datetime.timedelta(days=3650)
>>> ten_years.days // 365
10
>>> nine_years = ten_years - year
>>> nine_years
datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 3)
									

date 对象 ¶

A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions.

January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. 2

class datetime. date ( year , month , day ) ¶

All arguments are required. Arguments must be integers, in the following ranges:

• MINYEAR <= year <= MAXYEAR

• 1 <= month <= 12

• 1 <= day <= number of days in the given month and year

若给定自变量在那些范围之外， ValueError 被引发。

其它构造函数，所有类方法：

classmethod date. today ( ) ¶

Return the current local date.

这相当于 date.fromtimestamp(time.time()) .

classmethod date. fromtimestamp ( timestamp ) ¶

Return the local date corresponding to the POSIX timestamp, such as is returned by time.time() .

This may raise OverflowError , if the timestamp is out of the range of values supported by the platform C localtime() function, and OSError on localtime() failure. It’s common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp() .

3.3 版改变： 引发 OverflowError 而不是 ValueError if the timestamp is out of the range of values supported by the platform C localtime() function. Raise OSError 而不是 ValueError on localtime() failure.

classmethod date. fromordinal ( ordinal ) ¶

Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1.

ValueError is raised unless 1 <= ordinal <= date.max.toordinal() . For any date d , date.fromordinal(d.toordinal()) == d .

classmethod date. fromisoformat ( date_string ) ¶

返回 date corresponding to a date_string given in the format YYYY-MM-DD :

>>> from datetime import date
>>> date.fromisoformat('2019-12-04')
datetime.date(2019, 12, 4)
										

This is the inverse of date.isoformat() . It only supports the format YYYY-MM-DD .

3.7 版新增。

classmethod date. fromisocalendar ( year , week , day ) ¶

返回 date corresponding to the ISO calendar date specified by year, week and day. This is the inverse of the function date.isocalendar() .

3.8 版新增。

类属性：

date. min ¶

The earliest representable date, date(MINYEAR, 1, 1) .

date. max ¶

The latest representable date, date(MAXYEAR, 12, 31) .

date. resolution ¶

The smallest possible difference between non-equal date objects, timedelta(days=1) .

实例属性 (只读)：

date. year ¶

Between MINYEAR and MAXYEAR 包含在内。

date. month ¶

在 1 至 12 (含 12) 之间。

date. day ¶

Between 1 and the number of days in the given month of the given year.

支持的操作：

注意事项：

1. date2 is moved forward in time if timedelta.days > 0 , or backward if timedelta.days < 0 . Afterward date2 - date1 == timedelta.days . timedelta.seconds and timedelta.microseconds 被忽略。 OverflowError 被引发若 date2.year would be smaller than MINYEAR or larger than MAXYEAR .

2. timedelta.seconds and timedelta.microseconds 被忽略。

3. This is exact, and cannot overflow. timedelta.seconds and timedelta.microseconds are 0, and date2 + timedelta == date1 after.

4. In other words, date1 < date2 if and only if date1.toordinal() < date2.toordinal() . Date comparison raises TypeError if the other comparand isn’t also a date object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a date object is compared to an object of a different type, TypeError is raised unless the comparison is == or != . The latter cases return False or True ，分别。

In Boolean contexts, all date objects are considered to be true.

实例方法：

date. replace ( year=self.year , month=self.month , day=self.day ) ¶

Return a date with the same value, except for those parameters given new values by whichever keyword arguments are specified.

范例：

>>> from datetime import date
>>> d = date(2002, 12, 31)
>>> d.replace(day=26)
datetime.date(2002, 12, 26)
										

date. timetuple ( ) ¶

返回 time.struct_time such as returned by time.localtime() .

The hours, minutes and seconds are 0, and the DST flag is -1.

d.timetuple() 相当于：

time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
										

where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st.

date. toordinal ( ) ¶

Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d , date.fromordinal(d.toordinal()) == d .

date. weekday ( ) ¶

Return the day of the week as an integer, where Monday is 0 and Sunday is 6. For example, date(2002, 12, 4).weekday() == 2 , a Wednesday. See also isoweekday() .

date. isoweekday ( ) ¶

Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example, date(2002, 12, 4).isoweekday() == 3 , a Wednesday. See also weekday() , isocalendar() .

date. isocalendar ( ) ¶

返回 命名元组 object with three components: year , week and weekday .

The ISO calendar is a widely used variant of the Gregorian calendar. 3

The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year.

For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004:

>>> from datetime import date
>>> date(2003, 12, 29).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=1)
>>> date(2004, 1, 4).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=7)
										

3.9 版改变： Result changed from a tuple to a 命名元组 .

date. isoformat ( ) ¶

Return a string representing the date in ISO 8601 format, YYYY-MM-DD :

>>> from datetime import date
>>> date(2002, 12, 4).isoformat()
'2002-12-04'
										

This is the inverse of date.fromisoformat() .

date. __str__ ( ) ¶

For a date d , str(d) 相当于 d.isoformat() .

date. ctime ( ) ¶

Return a string representing the date:

>>> from datetime import date
>>> date(2002, 12, 4).ctime()
'Wed Dec  4 00:00:00 2002'
										

d.ctime() 相当于：

time.ctime(time.mktime(d.timetuple()))
										

on platforms where the native C ctime() function (which time.ctime() invokes, but which date.ctime() does not invoke) conforms to the C standard.

date. strftime ( format ) ¶

Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

date. __format__ ( format ) ¶

如同 date.strftime() . This makes it possible to specify a format string for a date object in 格式化字符串文字 and when using str.format() . For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

>>> import time
>>> from datetime import date
>>> today = date.today()
>>> today
datetime.date(2007, 12, 5)
>>> today == date.fromtimestamp(time.time())
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
...     my_birthday = my_birthday.replace(year=today.year + 1)
>>> my_birthday
datetime.date(2008, 6, 24)
>>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202
									

>>> from datetime import date
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)
>>> # Methods related to formatting string output
>>> d.isoformat()
'2002-03-11'
>>> d.strftime("%d/%m/%y")
'11/03/02'
>>> d.strftime("%A %d. %B %Y")
'Monday 11. March 2002'
>>> d.ctime()
'Mon Mar 11 00:00:00 2002'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
'The day is 11, the month is March.'
>>> # Methods for to extracting 'components' under different calendars
>>> t = d.timetuple()
>>> for i in t:
...     print(i)
2002                # year
3                   # month
11                  # day
0
0
0
0                   # weekday (0 = Monday)
70                  # 70th day in the year
-1
>>> ic = d.isocalendar()
>>> for i in ic:
...     print(i)
2002                # ISO year
11                  # ISO week number
1                   # ISO day number ( 1 = Monday )
>>> # A date object is immutable; all operations produce a new object
>>> d.replace(year=2005)
datetime.date(2005, 3, 11)
									

datetime 对象 ¶

A datetime object is a single object containing all the information from a date object and a time 对象。

Like a date 对象， datetime assumes the current Gregorian calendar extended in both directions; like a time 对象， datetime assumes there are exactly 3600*24 seconds in every day.

构造函数：

class datetime. datetime ( year , month , day , hour=0 , minute=0 , second=0 , microsecond=0 , tzinfo=None , * , fold=0 ) ¶

year , month and day arguments are required. tzinfo 可以是 None , or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:

• MINYEAR <= year <= MAXYEAR ,

• 1 <= month <= 12 ,

• 1 <= day <= number of days in the given month and year ,

• 0 <= hour < 24 ,

• 0 <= minute < 60 ,

• 0 <= second < 60 ,

• 0 <= microsecond < 1000000 ,

• fold in [0, 1] .

若给定自变量在那些范围之外， ValueError 被引发。

3.6 版新增： 添加 fold 自变量。

其它构造函数，所有类方法：

classmethod datetime. today ( ) ¶

Return the current local datetime, with tzinfo None .

等效于：

datetime.fromtimestamp(time.time())
										

另请参阅 now() , fromtimestamp() .

This method is functionally equivalent to now() , but without a tz 参数。

classmethod datetime. now ( tz=None ) ¶

Return the current local date and time.

If optional argument tz is None or not specified, this is like today() , but, if possible, supplies more precision than can be gotten from going through a time.time() timestamp (for example, this may be possible on platforms supplying the C gettimeofday() function).

若 tz 不是 None , it must be an instance of a tzinfo subclass, and the current date and time are converted to tz ’s time zone.

This function is preferred over today() and utcnow() .

classmethod datetime. utcnow ( ) ¶

Return the current UTC date and time, with tzinfo None .

这像 now() , but returns the current UTC date and time, as a naive datetime object. An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc) 。另请参阅 now() .

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing the current time in UTC is by calling datetime.now(timezone.utc) .

classmethod datetime. fromtimestamp ( timestamp , tz=None ) ¶

Return the local date and time corresponding to the POSIX timestamp, such as is returned by time.time() . If optional argument tz is None or not specified, the timestamp is converted to the platform’s local date and time, and the returned datetime object is naive.

若 tz 不是 None , it must be an instance of a tzinfo subclass, and the timestamp is converted to tz ’s time zone.

fromtimestamp() 可能引发 OverflowError , if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions, and OSError on localtime() or gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp() , and then it’s possible to have two timestamps differing by a second that yield identical datetime objects. This method is preferred over utcfromtimestamp() .

3.3 版改变： 引发 OverflowError 而不是 ValueError if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions. Raise OSError 而不是 ValueError on localtime() or gmtime() failure.

3.6 版改变： fromtimestamp() may return instances with fold set to 1.

classmethod datetime. utcfromtimestamp ( timestamp ) ¶

Return the UTC datetime corresponding to the POSIX timestamp, with tzinfo None . (The resulting object is naive.)

This may raise OverflowError , if the timestamp is out of the range of values supported by the platform C gmtime() function, and OSError on gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038.

To get an aware datetime object, call fromtimestamp() :

datetime.fromtimestamp(timestamp, timezone.utc)
										

On the POSIX compliant platforms, it is equivalent to the following expression:

datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)
										

except the latter formula always supports the full years range: between MINYEAR and MAXYEAR 包含在内。

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing a specific timestamp in UTC is by calling datetime.fromtimestamp(timestamp, tz=timezone.utc) .

3.3 版改变： 引发 OverflowError 而不是 ValueError if the timestamp is out of the range of values supported by the platform C gmtime() function. Raise OSError 而不是 ValueError on gmtime() failure.

classmethod datetime. fromordinal ( ordinal ) ¶

返回 datetime corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <= datetime.max.toordinal() . The hour, minute, second and microsecond of the result are all 0, and tzinfo is None .

classmethod datetime. combine ( date , time , tzinfo=self.tzinfo ) ¶

返回新的 datetime object whose date components are equal to the given date object’s, and whose time components are equal to the given time object’s. If the tzinfo argument is provided, its value is used to set the tzinfo attribute of the result, otherwise the tzinfo 属性在 time argument is used.

For any datetime object d , d == datetime.combine(d.date(), d.time(), d.tzinfo) . If date is a datetime object, its time components and tzinfo attributes are ignored.

3.6 版改变： 添加 tzinfo 自变量。

classmethod datetime. fromisoformat ( date_string ) ¶

返回 datetime corresponding to a date_string in one of the formats emitted by date.isoformat() and datetime.isoformat() .

Specifically, this function supports strings in the format:

YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]]
										

where * can match any single character.

Caution

This does not support parsing arbitrary ISO 8601 strings - it is only intended as the inverse operation of datetime.isoformat() . A more full-featured ISO 8601 parser, dateutil.parser.isoparse is available in the third-party package dateutil .

范例：

>>> from datetime import datetime
>>> datetime.fromisoformat('2011-11-04')
datetime.datetime(2011, 11, 4, 0, 0)
>>> datetime.fromisoformat('2011-11-04T00:05:23')
datetime.datetime(2011, 11, 4, 0, 5, 23)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283+00:00')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc)
>>> datetime.fromisoformat('2011-11-04T00:05:23+04:00')
datetime.datetime(2011, 11, 4, 0, 5, 23,
    tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
										

3.7 版新增。

classmethod datetime. fromisocalendar ( year , week , day ) ¶

返回 datetime corresponding to the ISO calendar date specified by year, week and day. The non-date components of the datetime are populated with their normal default values. This is the inverse of the function datetime.isocalendar() .

3.8 版新增。

classmethod datetime. strptime ( date_string , format ) ¶

返回 datetime corresponding to date_string , parsed according to format .

这相当于：

datetime(*(time.strptime(date_string, format)[0:6]))
										

ValueError is raised if the date_string and format can’t be parsed by time.strptime() or if it returns a value which isn’t a time tuple. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

类属性：

datetime. min ¶

The earliest representable datetime , datetime(MINYEAR, 1, 1, tzinfo=None) .

datetime. max ¶

The latest representable datetime , datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999, tzinfo=None) .

datetime. resolution ¶

The smallest possible difference between non-equal datetime objects, timedelta(microseconds=1) .

实例属性 (只读)：

datetime. year ¶

Between MINYEAR and MAXYEAR 包含在内。

datetime. month ¶

在 1 至 12 (含 12) 之间。

datetime. day ¶

Between 1 and the number of days in the given month of the given year.

datetime. hour ¶

在 range(24) .

datetime. minute ¶

在 range(60) .

datetime. second ¶

在 range(60) .

datetime. microsecond ¶

在 range(1000000) .

datetime. tzinfo ¶

The object passed as the tzinfo 自变量到 datetime constructor, or None if none was passed.

datetime. fold ¶

在 [0, 1] . Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.

3.6 版新增。

支持的操作：

1. datetime2 is a duration of timedelta removed from datetime1, moving forward in time if timedelta.days > 0, or backward if timedelta.days < 0. The result has the same tzinfo attribute as the input datetime, and datetime2 - datetime1 == timedelta after. OverflowError is raised if datetime2.year would be smaller than MINYEAR or larger than MAXYEAR . Note that no time zone adjustments are done even if the input is an aware object.

2. Computes the datetime2 such that datetime2 + timedelta == datetime1. As for addition, the result has the same tzinfo attribute as the input datetime, and no time zone adjustments are done even if the input is aware.

3. Subtraction of a datetime from a datetime is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive, TypeError 被引发。

   If both are naive, or both are aware and have the same tzinfo attribute, the tzinfo attributes are ignored, and the result is a timedelta object t 这样 datetime2 + t == datetime1 . No time zone adjustments are done in this case.

   If both are aware and have different tzinfo attributes, a-b acts as if a and b were first converted to naive UTC datetimes first. The result is (a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None) - b.utcoffset()) except that the implementation never overflows.

4. datetime1 is considered less than datetime2 when datetime1 precedes datetime2 in time.

   If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.

   If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base datetimes are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset() ).

   3.3 版改变： Equality comparisons between aware and naive datetime instances don’t raise TypeError .

   注意

   In order to stop comparison from falling back to the default scheme of comparing object addresses, datetime comparison normally raises TypeError if the other comparand isn’t also a datetime object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a datetime object is compared to an object of a different type, TypeError is raised unless the comparison is == or != . The latter cases return False or True ，分别。

实例方法：

datetime. date ( ) ¶

返回 date object with same year, month and day.

datetime. time ( ) ¶

返回 time object with same hour, minute, second, microsecond and fold. tzinfo is None . See also method timetz() .

3.6 版改变： The fold value is copied to the returned time 对象。

datetime. timetz ( ) ¶

返回 time object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method time() .

3.6 版改变： The fold value is copied to the returned time 对象。

datetime. replace ( year=self.year , month=self.month , day=self.day , hour=self.hour , minute=self.minute , second=self.second , microsecond=self.microsecond , tzinfo=self.tzinfo , * , fold=0 ) ¶

Return a datetime with the same attributes, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive datetime from an aware datetime with no conversion of date and time data.

3.6 版新增： 添加 fold 自变量。

datetime. astimezone ( tz=None ) ¶

返回 datetime object with new tzinfo 属性 tz , adjusting the date and time data so the result is the same UTC time as self , but in tz ’s local time.

If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None 。若 self is naive, it is presumed to represent time in the system timezone.

If called without arguments (or with tz=None ) the system local timezone is assumed for the target timezone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS.

若 self.tzinfo is tz , self.astimezone(tz) 等于 self : no adjustment of date or time data is performed. Else the result is local time in the timezone tz , representing the same UTC time as self : after astz = dt.astimezone(tz) , astz - astz.utcoffset() will have the same date and time data as dt - dt.utcoffset() .

If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data, use dt.replace(tzinfo=tz) . If you merely want to remove the time zone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None) .

Note that the default tzinfo.fromutc() method can be overridden in a tzinfo subclass to affect the result returned by astimezone() . Ignoring error cases, astimezone() acts like:

def astimezone(self, tz):
    if self.tzinfo is tz:
        return self
    # Convert self to UTC, and attach the new time zone object.
    utc = (self - self.utcoffset()).replace(tzinfo=tz)
    # Convert from UTC to tz's local time.
    return tz.fromutc(utc)
										

3.3 版改变： tz now can be omitted.

3.6 版改变： astimezone() method can now be called on naive instances that are presumed to represent system local time.

datetime. utcoffset ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.utcoffset(self) , and raises an exception if the latter doesn’t return None 或 timedelta object with magnitude less than one day.

3.7 版改变： The UTC offset is not restricted to a whole number of minutes.

datetime. dst ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.dst(self) , and raises an exception if the latter doesn’t return None 或 timedelta object with magnitude less than one day.

3.7 版改变： The DST offset is not restricted to a whole number of minutes.

datetime. tzname ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.tzname(self) , raises an exception if the latter doesn’t return None or a string object,

datetime. timetuple ( ) ¶

返回 time.struct_time such as returned by time.localtime() .

d.timetuple() 相当于：

time.struct_time((d.year, d.month, d.day,
                  d.hour, d.minute, d.second,
                  d.weekday(), yday, dst))
										

where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st. The tm_isdst flag of the result is set according to the dst() 方法： tzinfo is None or dst() 返回 None , tm_isdst 被设为 -1 ; else if dst() returns a non-zero value, tm_isdst 被设为 1 ; else tm_isdst 被设为 0 .

datetime. utctimetuple ( ) ¶

若 datetime instance d is naive, this is the same as d.timetuple() 除了 tm_isdst is forced to 0 regardless of what d.dst() returns. DST is never in effect for a UTC time.

若 d is aware, d is normalized to UTC time, by subtracting d.utcoffset() ，和 time.struct_time for the normalized time is returned. tm_isdst is forced to 0. Note that an OverflowError 可能被引发若 d .year was MINYEAR or MAXYEAR and UTC adjustment spills over a year boundary.

警告

Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC; as a result, using utcfromtimetuple may give misleading results. If you have a naive datetime representing UTC, use datetime.replace(tzinfo=timezone.utc) to make it aware, at which point you can use datetime.timetuple() .

datetime. toordinal ( ) ¶

Return the proleptic Gregorian ordinal of the date. The same as self.date().toordinal() .

datetime. timestamp ( ) ¶

Return POSIX timestamp corresponding to the datetime instance. The return value is a float similar to that returned by time.time() .

Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime() function to perform the conversion. Since datetime supports wider range of values than mktime() on many platforms, this method may raise OverflowError for times far in the past or far in the future.

For aware datetime instances, the return value is computed as:

(dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
										

3.3 版新增。

3.6 版改变： timestamp() method uses the fold attribute to disambiguate the times during a repeated interval.

注意

There is no method to obtain the POSIX timestamp directly from a naive datetime instance representing UTC time. If your application uses this convention and your system timezone is not set to UTC, you can obtain the POSIX timestamp by supplying tzinfo=timezone.utc :

timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
											

or by calculating the timestamp directly:

timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)
											

datetime. weekday ( ) ¶

Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as self.date().weekday() 。另请参阅 isoweekday() .

datetime. isoweekday ( ) ¶

Return the day of the week as an integer, where Monday is 1 and Sunday is 7. The same as self.date().isoweekday() 。另请参阅 weekday() , isocalendar() .

datetime. isocalendar ( ) ¶

返回 命名元组 with three components: year , week and weekday . The same as self.date().isocalendar() .

datetime. isoformat ( sep='T' , timespec='auto' ) ¶

Return a string representing the date and time in ISO 8601 format:

• YYYY-MM-DDTHH:MM:SS.ffffff , if microsecond is not 0

• YYYY-MM-DDTHH:MM:SS , if microsecond is 0

若 utcoffset() 不返回 None , a string is appended, giving the UTC offset:

• YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]] , if microsecond is not 0

• YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]] , if microsecond is 0

范例：

>>> from datetime import datetime, timezone
>>> datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat()
'2019-05-18T15:17:08.132263'
>>> datetime(2019, 5, 18, 15, 17, tzinfo=timezone.utc).isoformat()
'2019-05-18T15:17:00+00:00'
										

可选自变量 sep (默认 'T' ) is a one-character separator, placed between the date and time portions of the result. For example:

>>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
...     """A time zone with an arbitrary, constant -06:39 offset."""
...     def utcoffset(self, dt):
...         return timedelta(hours=-6, minutes=-39)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
>>> datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat()
'2009-11-27T00:00:00.000100-06:39'
										

可选自变量 timespec specifies the number of additional components of the time to include (the default is 'auto' ). It can be one of the following:

• 'auto' : Same as 'seconds' if microsecond is 0, same as 'microseconds' 否则。

• 'hours' : Include the hour in the two-digit HH 格式。

• 'minutes' : Include hour and minute in HH:MM 格式。

• 'seconds' : Include hour , minute ，和 second in HH:MM:SS 格式。

• 'milliseconds' : Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss 格式。

• 'microseconds' : Include full time in HH:MM:SS.ffffff 格式。

注意

Excluded time components are truncated, not rounded.

ValueError will be raised on an invalid timespec argument:

>>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'
										

3.6 版新增： 添加 timespec 自变量。

datetime. __str__ ( ) ¶

For a datetime instance d , str(d) 相当于 d.isoformat(' ') .

datetime. ctime ( ) ¶

Return a string representing the date and time:

>>> from datetime import datetime
>>> datetime(2002, 12, 4, 20, 30, 40).ctime()
'Wed Dec  4 20:30:40 2002'
										

The output string will not include time zone information, regardless of whether the input is aware or naive.

d.ctime() 相当于：

time.ctime(time.mktime(d.timetuple()))
										

on platforms where the native C ctime() function (which time.ctime() invokes, but which datetime.ctime() does not invoke) conforms to the C standard.

datetime. strftime ( format ) ¶

Return a string representing the date and time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

datetime. __format__ ( format ) ¶

如同 datetime.strftime() . This makes it possible to specify a format string for a datetime object in 格式化字符串文字 and when using str.format() . For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

>>> from datetime import datetime, date, time, timezone
>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)
>>> # Using datetime.now()
>>> datetime.now()
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043)   # GMT +1
>>> datetime.now(timezone.utc)
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060, tzinfo=datetime.timezone.utc)
>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)
>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt:
...     print(it)
...
2006    # year
11      # month
21      # day
16      # hour
30      # minute
0       # second
1       # weekday (0 = Monday)
325     # number of days since 1st January
-1      # dst - method tzinfo.dst() returned None
>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic:
...     print(it)
...
2006    # ISO year
47      # ISO week
2       # ISO weekday
>>> # Formatting a datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'
									

from datetime import timedelta, datetime, tzinfo, timezone
class KabulTz(tzinfo):
    # Kabul used +4 until 1945, when they moved to +4:30
    UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)
    def utcoffset(self, dt):
        if dt.year < 1945:
            return timedelta(hours=4)
        elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
            # An ambiguous ("imaginary") half-hour range representing
            # a 'fold' in time due to the shift from +4 to +4:30.
            # If dt falls in the imaginary range, use fold to decide how
            # to resolve. See PEP495.
            return timedelta(hours=4, minutes=(30 if dt.fold else 0))
        else:
            return timedelta(hours=4, minutes=30)
    def fromutc(self, dt):
        # Follow same validations as in datetime.tzinfo
        if not isinstance(dt, datetime):
            raise TypeError("fromutc() requires a datetime argument")
        if dt.tzinfo is not self:
            raise ValueError("dt.tzinfo is not self")
        # A custom implementation is required for fromutc as
        # the input to this function is a datetime with utc values
        # but with a tzinfo set to self.
        # See datetime.astimezone or fromtimestamp.
        if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
            return dt + timedelta(hours=4, minutes=30)
        else:
            return dt + timedelta(hours=4)
    def dst(self, dt):
        # Kabul does not observe daylight saving time.
        return timedelta(0)
    def tzname(self, dt):
        if dt >= self.UTC_MOVE_DATE:
            return "+04:30"
        return "+04"
									

>>> tz1 = KabulTz()
>>> # Datetime before the change
>>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
>>> print(dt1.utcoffset())
4:00:00
>>> # Datetime after the change
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
>>> print(dt2.utcoffset())
4:30:00
>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(timezone.utc)
>>> dt3
datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
>>> dt2
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
>>> dt2 == dt3
True
									

time 对象 ¶

A time object represents a (local) time of day, independent of any particular day, and subject to adjustment via a tzinfo 对象。

class datetime. time ( hour=0 , minute=0 , second=0 , microsecond=0 , tzinfo=None , * , fold=0 ) ¶

All arguments are optional. tzinfo 可以是 None , or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:

• 0 <= hour < 24 ,

• 0 <= minute < 60 ,

• 0 <= second < 60 ,

• 0 <= microsecond < 1000000 ,

• fold in [0, 1] .

若给定自变量在那些范围之外， ValueError is raised. All default to 0 except tzinfo ，其默认为 None .

类属性：

time. min ¶

The earliest representable time , time(0, 0, 0, 0) .

time. max ¶

The latest representable time , time(23, 59, 59, 999999) .

time. resolution ¶

The smallest possible difference between non-equal time objects, timedelta(microseconds=1) , although note that arithmetic on time objects is not supported.

实例属性 (只读)：

time. hour ¶

在 range(24) .

time. minute ¶

在 range(60) .

time. second ¶

在 range(60) .

time. microsecond ¶

在 range(1000000) .

time. tzinfo ¶

The object passed as the tzinfo argument to the time constructor, or None if none was passed.

time. fold ¶

在 [0, 1] . Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation.

3.6 版新增。

time objects support comparison of time to time ，其中 a is considered less than b when a precedes b in time. If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances.

If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base times are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset() ). In order to stop mixed-type comparisons from falling back to the default comparison by object address, when a time object is compared to an object of a different type, TypeError is raised unless the comparison is == or != . The latter cases return False or True ，分别。

In Boolean contexts, a time object is always considered to be true.

Other constructor:

classmethod time. fromisoformat ( time_string ) ¶

返回 time corresponding to a time_string in one of the formats emitted by time.isoformat() . Specifically, this function supports strings in the format:

HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]
										

Caution

This does not support parsing arbitrary ISO 8601 strings. It is only intended as the inverse operation of time.isoformat() .

范例：

>>> from datetime import time
>>> time.fromisoformat('04:23:01')
datetime.time(4, 23, 1)
>>> time.fromisoformat('04:23:01.000384')
datetime.time(4, 23, 1, 384)
>>> time.fromisoformat('04:23:01+04:00')
datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
										

3.7 版新增。

实例方法：

time. replace ( hour=self.hour , minute=self.minute , second=self.second , microsecond=self.microsecond , tzinfo=self.tzinfo , * , fold=0 ) ¶

返回 time with the same value, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive time from an aware time , without conversion of the time data.

3.6 版新增： 添加 fold 自变量。

time. isoformat ( timespec='auto' ) ¶

Return a string representing the time in ISO 8601 format, one of:

• HH:MM:SS.ffffff , if microsecond is not 0

• HH:MM:SS , if microsecond is 0

• HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]] , if utcoffset() 不返回 None

• HH:MM:SS+HH:MM[:SS[.ffffff]] , if microsecond is 0 and utcoffset() 不返回 None

可选自变量 timespec specifies the number of additional components of the time to include (the default is 'auto' ). It can be one of the following:

• 'auto' : Same as 'seconds' if microsecond is 0, same as 'microseconds' 否则。

• 'hours' : Include the hour in the two-digit HH 格式。

• 'minutes' : Include hour and minute in HH:MM 格式。

• 'seconds' : Include hour , minute ，和 second in HH:MM:SS 格式。

• 'milliseconds' : Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss 格式。

• 'microseconds' : Include full time in HH:MM:SS.ffffff 格式。

注意

Excluded time components are truncated, not rounded.

ValueError will be raised on an invalid timespec 自变量。

范例：

>>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'
										

3.6 版新增： 添加 timespec 自变量。

time. __str__ ( ) ¶

For a time t , str(t) 相当于 t.isoformat() .

time. strftime ( format ) ¶

Return a string representing the time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

time. __format__ ( format ) ¶

如同 time.strftime() . This makes it possible to specify a format string for a time object in 格式化字符串文字 and when using str.format() . For a complete list of formatting directives, see strftime() 和 strptime() 行为 .

time. utcoffset ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.utcoffset(None) , and raises an exception if the latter doesn’t return None 或 timedelta object with magnitude less than one day.

3.7 版改变： The UTC offset is not restricted to a whole number of minutes.

time. dst ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.dst(None) , and raises an exception if the latter doesn’t return None ，或 timedelta object with magnitude less than one day.

3.7 版改变： The DST offset is not restricted to a whole number of minutes.

time. tzname ( ) ¶

若 tzinfo is None , returns None , else returns self.tzinfo.tzname(None) , or raises an exception if the latter doesn’t return None or a string object.

>>> from datetime import time, tzinfo, timedelta
>>> class TZ1(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=1)
...     def dst(self, dt):
...         return timedelta(0)
...     def tzname(self,dt):
...         return "+01:00"
...     def  __repr__(self):
...         return f"{self.__class__.__name__}()"
...
>>> t = time(12, 10, 30, tzinfo=TZ1())
>>> t
datetime.time(12, 10, 30, tzinfo=TZ1())
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'+01:00'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 +01:00'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'
									

tzinfo 对象 ¶

class datetime. tzinfo ¶

This is an abstract base class, meaning that this class should not be instantiated directly. Define a subclass of tzinfo to capture information about a particular time zone.

An instance of (a concrete subclass of) tzinfo can be passed to the constructors for datetime and time objects. The latter objects view their attributes as being in local time, and the tzinfo object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them.

You need to derive a concrete subclass, and (at least) supply implementations of the standard tzinfo methods needed by the datetime methods you use. The datetime 模块提供 timezone , a simple concrete subclass of tzinfo which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT.

Special requirement for pickling: A tzinfo subclass must have an __init__() method that can be called with no arguments, otherwise it can be pickled but possibly not unpickled again. This is a technical requirement that may be relaxed in the future.

A concrete subclass of tzinfo may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware datetime objects. If in doubt, simply implement all of them.

tzinfo. utcoffset ( dt ) ¶

Return offset of local time from UTC, as a timedelta object that is positive east of UTC. If local time is west of UTC, this should be negative.

This represents the total offset from UTC; for example, if a tzinfo object represents both time zone and DST adjustments, utcoffset() should return their sum. If the UTC offset isn’t known, return None . Else the value returned must be a timedelta object strictly between -timedelta(hours=24) and timedelta(hours=24) (the magnitude of the offset must be less than one day). Most implementations of utcoffset() will probably look like one of these two:

return CONSTANT                 # fixed-offset class
return CONSTANT + self.dst(dt)  # daylight-aware class
										

若 utcoffset() 不返回 None , dst() should not return None either.

The default implementation of utcoffset() 引发 NotImplementedError .

3.7 版改变： The UTC offset is not restricted to a whole number of minutes.

tzinfo. dst ( dt ) ¶

Return the daylight saving time (DST) adjustment, as a timedelta object or None if DST information isn’t known.

返回 timedelta(0) if DST is not in effect. If DST is in effect, return the offset as a timedelta object (see utcoffset() for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by utcoffset() , so there’s no need to consult dst() unless you’re interested in obtaining DST info separately. For example, datetime.timetuple() calls its tzinfo attribute’s dst() method to determine how the tm_isdst flag should be set, and tzinfo.fromutc() 调用 dst() to account for DST changes when crossing time zones.

An instance tz of a tzinfo subclass that models both standard and daylight times must be consistent in this sense:

tz.utcoffset(dt) - tz.dst(dt)

must return the same result for every datetime dt with dt.tzinfo == tz For sane tzinfo subclasses, this expression yields the time zone’s “standard offset”, which should not depend on the date or the time, but only on geographic location. The implementation of datetime.astimezone() relies on this, but cannot detect violations; it’s the programmer’s responsibility to ensure it. If a tzinfo subclass cannot guarantee this, it may be able to override the default implementation of tzinfo.fromutc() to work correctly with astimezone() regardless.

Most implementations of dst() will probably look like one of these two:

def dst(self, dt):
    # a fixed-offset class:  doesn't account for DST
    return timedelta(0)
										

或：

def dst(self, dt):
    # Code to set dston and dstoff to the time zone's DST
    # transition times based on the input dt.year, and expressed
    # in standard local time.
    if dston <= dt.replace(tzinfo=None) < dstoff:
        return timedelta(hours=1)
    else:
        return timedelta(0)
										

The default implementation of dst() 引发 NotImplementedError .

3.7 版改变： The DST offset is not restricted to a whole number of minutes.

tzinfo. tzname ( dt ) ¶

Return the time zone name corresponding to the datetime object dt , as a string. Nothing about string names is defined by the datetime module, and there’s no requirement that it mean anything in particular. For example, “GMT”, “UTC”, “-500”, “-5:00”, “EDT”, “US/Eastern”, “America/New York” are all valid replies. Return None if a string name isn’t known. Note that this is a method rather than a fixed string primarily because some tzinfo subclasses will wish to return different names depending on the specific value of dt passed, especially if the tzinfo class is accounting for daylight time.

The default implementation of tzname() 引发 NotImplementedError .

These methods are called by a datetime or time object, in response to their methods of the same names. A datetime object passes itself as the argument, and a time object passes None as the argument. A tzinfo subclass’s methods should therefore be prepared to accept a dt argument of None , or of class datetime .

当 None is passed, it’s up to the class designer to decide the best response. For example, returning None is appropriate if the class wishes to say that time objects don’t participate in the tzinfo protocols. It may be more useful for utcoffset(None) to return the standard UTC offset, as there is no other convention for discovering the standard offset.

当 datetime object is passed in response to a datetime 方法， dt.tzinfo is the same object as self . tzinfo methods can rely on this, unless user code calls tzinfo methods directly. The intent is that the tzinfo methods interpret dt as being in local time, and not need worry about objects in other timezones.

There is one more tzinfo method that a subclass may wish to override:

tzinfo. fromutc ( dt ) ¶

This is called from the default datetime.astimezone() implementation. When called from that, dt.tzinfo is self ，和 dt ’s date and time data are to be viewed as expressing a UTC time. The purpose of fromutc() is to adjust the date and time data, returning an equivalent datetime in self ’s local time.

Most tzinfo subclasses should be able to inherit the default fromutc() implementation without problems. It’s strong enough to handle fixed-offset time zones, and time zones accounting for both standard and daylight time, and the latter even if the DST transition times differ in different years. An example of a time zone the default fromutc() implementation may not handle correctly in all cases is one where the standard offset (from UTC) depends on the specific date and time passed, which can happen for political reasons. The default implementations of astimezone() and fromutc() may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes.

Skipping code for error cases, the default fromutc() implementation acts like:

def fromutc(self, dt):
    # raise ValueError error if dt.tzinfo is not self
    dtoff = dt.utcoffset()
    dtdst = dt.dst()
    # raise ValueError if dtoff is None or dtdst is None
    delta = dtoff - dtdst  # this is self's standard offset
    if delta:
        dt += delta   # convert to standard local time
        dtdst = dt.dst()
        # raise ValueError if dtdst is None
    if dtdst:
        return dt + dtdst
    else:
        return dt
										

In the following tzinfo_examples.py file there are some examples of tzinfo 类：

from datetime import tzinfo, timedelta, datetime
ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)
# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
#  timezones where UTC offset and/or the DST rules had
#  changed in the past.)
import time as _time
STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
    DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
    DSTOFFSET = STDOFFSET
DSTDIFF = DSTOFFSET - STDOFFSET
class LocalTimezone(tzinfo):
    def fromutc(self, dt):
        assert dt.tzinfo is self
        stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
        args = _time.localtime(stamp)[:6]
        dst_diff = DSTDIFF // SECOND
        # Detect fold
        fold = (args == _time.localtime(stamp - dst_diff))
        return datetime(*args, microsecond=dt.microsecond,
                        tzinfo=self, fold=fold)
    def utcoffset(self, dt):
        if self._isdst(dt):
            return DSTOFFSET
        else:
            return STDOFFSET
    def dst(self, dt):
        if self._isdst(dt):
            return DSTDIFF
        else:
            return ZERO
    def tzname(self, dt):
        return _time.tzname[self._isdst(dt)]
    def _isdst(self, dt):
        tt = (dt.year, dt.month, dt.day,
              dt.hour, dt.minute, dt.second,
              dt.weekday(), 0, 0)
        stamp = _time.mktime(tt)
        tt = _time.localtime(stamp)
        return tt.tm_isdst > 0
Local = LocalTimezone()
# A complete implementation of current DST rules for major US time zones.
def first_sunday_on_or_after(dt):
    days_to_go = 6 - dt.weekday()
    if days_to_go:
        dt += timedelta(days_to_go)
    return dt
# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# http://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006
def us_dst_range(year):
    # Find start and end times for US DST. For years before 1967, return
    # start = end for no DST.
    if 2006 < year:
        dststart, dstend = DSTSTART_2007, DSTEND_2007
    elif 1986 < year < 2007:
        dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
    elif 1966 < year < 1987:
        dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
    else:
        return (datetime(year, 1, 1), ) * 2
    start = first_sunday_on_or_after(dststart.replace(year=year))
    end = first_sunday_on_or_after(dstend.replace(year=year))
    return start, end
class USTimeZone(tzinfo):
    def __init__(self, hours, reprname, stdname, dstname):
        self.stdoffset = timedelta(hours=hours)
        self.reprname = reprname
        self.stdname = stdname
        self.dstname = dstname
    def __repr__(self):
        return self.reprname
    def tzname(self, dt):
        if self.dst(dt):
            return self.dstname
        else:
            return self.stdname
    def utcoffset(self, dt):
        return self.stdoffset + self.dst(dt)
    def dst(self, dt):
        if dt is None or dt.tzinfo is None:
            # An exception may be sensible here, in one or both cases.
            # It depends on how you want to treat them.  The default
            # fromutc() implementation (called by the default astimezone()
            # implementation) passes a datetime with dt.tzinfo is self.
            return ZERO
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        # Can't compare naive to aware objects, so strip the timezone from
        # dt first.
        dt = dt.replace(tzinfo=None)
        if start + HOUR <= dt < end - HOUR:
            # DST is in effect.
            return HOUR
        if end - HOUR <= dt < end:
            # Fold (an ambiguous hour): use dt.fold to disambiguate.
            return ZERO if dt.fold else HOUR
        if start <= dt < start + HOUR:
            # Gap (a non-existent hour): reverse the fold rule.
            return HOUR if dt.fold else ZERO
        # DST is off.
        return ZERO
    def fromutc(self, dt):
        assert dt.tzinfo is self
        start, end = us_dst_range(dt.year)
        start = start.replace(tzinfo=self)
        end = end.replace(tzinfo=self)
        std_time = dt + self.stdoffset
        dst_time = std_time + HOUR
        if end <= dst_time < end + HOUR:
            # Repeated hour
            return std_time.replace(fold=1)
        if std_time < start or dst_time >= end:
            # Standard time
            return std_time
        if start <= std_time < end - HOUR:
            # Daylight saving time
            return dst_time
Eastern  = USTimeZone(-5, "Eastern",  "EST", "EDT")
Central  = USTimeZone(-6, "Central",  "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific  = USTimeZone(-8, "Pacific",  "PST", "PDT")
								

Note that there are unavoidable subtleties twice per year in a tzinfo subclass accounting for both standard and daylight time, at the DST transition points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the minute after 1:59 (EST) on the second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November:

  UTC   3:MM  4:MM  5:MM  6:MM  7:MM  8:MM
  EST  22:MM 23:MM  0:MM  1:MM  2:MM  3:MM
  EDT  23:MM  0:MM  1:MM  2:MM  3:MM  4:MM
start  22:MM 23:MM  0:MM  1:MM  3:MM  4:MM
  end  23:MM  0:MM  1:MM  1:MM  2:MM  3:MM
								

When DST starts (the “start” line), the local wall clock leaps from 1:59 to 3:00. A wall time of the form 2:MM doesn’t really make sense on that day, so astimezone(Eastern) won’t deliver a result with hour == 2 on the day DST begins. For example, at the Spring forward transition of 2016, we get:

>>> from datetime import datetime, timezone
>>> from tzinfo_examples import HOUR, Eastern
>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT
								

When DST ends (the “end” line), there’s a potentially worse problem: there’s an hour that can’t be spelled unambiguously in local wall time: the last hour of daylight time. In Eastern, that’s times of the form 5:MM UTC on the day daylight time ends. The local wall clock leaps from 1:59 (daylight time) back to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous. astimezone() mimics the local clock’s behavior by mapping two adjacent UTC hours into the same local hour then. In the Eastern example, UTC times of the form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times have the fold attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get:

>>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
...     u = u0 + i*HOUR
...     t = u.astimezone(Eastern)
...     print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
								

注意， datetime instances that differ only by the value of the fold attribute are considered equal in comparisons.

Applications that can’t bear wall-time ambiguities should explicitly check the value of the fold attribute or avoid using hybrid tzinfo subclasses; there are no ambiguities when using timezone , or any other fixed-offset tzinfo subclass (such as a class representing only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).

timezone 对象 ¶

timezone 类是子类化的 tzinfo , each instance of which represents a timezone defined by a fixed offset from UTC.

Objects of this class cannot be used to represent timezone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time.

class datetime. timezone ( offset , name=None ) ¶

offset argument must be specified as a timedelta object representing the difference between the local time and UTC. It must be strictly between -timedelta(hours=24) and timedelta(hours=24) , otherwise ValueError 被引发。

name argument is optional. If specified it must be a string that will be used as the value returned by the datetime.tzname() 方法。

3.2 版新增。

3.7 版改变： The UTC offset is not restricted to a whole number of minutes.

timezone. utcoffset ( dt ) ¶

Return the fixed value specified when the timezone instance is constructed.

dt argument is ignored. The return value is a timedelta instance equal to the difference between the local time and UTC.

3.7 版改变： The UTC offset is not restricted to a whole number of minutes.

timezone. tzname ( dt ) ¶

Return the fixed value specified when the timezone instance is constructed.

若 name is not provided in the constructor, the name returned by tzname(dt) is generated from the value of the offset as follows. If offset is timedelta(0) , the name is “UTC”, otherwise it is a string in the format UTC±HH:MM , where ± is the sign of offset , HH and MM are two digits of offset.hours and offset.minutes 分别。

3.6 版改变： Name generated from offset=timedelta(0) is now plain ‘UTC’ , not 'UTC+00:00' .

timezone. dst ( dt ) ¶

始终返回 None .

timezone. fromutc ( dt ) ¶

返回 dt + offset 。 dt argument must be an aware datetime instance, with tzinfo 设为 self .

类属性：

timezone. utc ¶

The UTC timezone, timezone(timedelta(0)) .

strftime() and strptime() 行为 ¶

date , datetime ，和 time objects all support a strftime(format) method, to create a string representing the time under the control of an explicit format string.

Conversely, the datetime.strptime() class method creates a datetime object from a string representing a date and time and a corresponding format string.

The table below provides a high-level comparison of strftime() versus strptime() :

datetime(*(time.strptime(date_string, format)[0:6]))