How to use Date and Time in Python
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Instance attributes read-only : datetime. This may raise , if the timestamp is out of the range of values supported by the platform C gmtime function.
Note that normalization of negative values may be surprising at first. If d is aware, d is normalized to UTC time, by subtracting d. If in doubt, simply implement all of them.
Import Datetime Library - If both comparands are aware, and have the same attribute, the common attribute is ignored and the base datetimes are compared. Changed in version 3.
While date and time arithmetic is supported, the focus of the implementation is on efficient attribute extraction for output formatting and manipulation. For related functionality, see also the and modules. An aware object has sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, to locate itself relative to other aware objects. An aware object is used to represent a specific moment in time that is not open to interpretation. 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, and objects have an optional time zone information attribute, tzinfo, that can be set to an instance of a subclass of the abstract class. These objects capture information about the offset from UTC time, the time zone name, and whether Daylight Saving Time is in effect. Note that only one concrete class, the class, is supplied by the module. The class can represent simple timezones with fixed offset 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. The module exports the following constants: datetime. MINYEAR The smallest year number allowed in a or object. MAXYEAR The largest year number allowed in a or object. Available Types class datetime. Attributes: , , and. Attributes: , , , , and. Attributes: , , , , , , , and. New in version 3. Objects of these types are immutable. Objects of the type are always naive. An object of type or may be naive or aware. A object d is aware if d. A object t is aware if t. Otherwise, t is naive. Subclass relationships: Objects A object represents a duration, the difference between two dates or times. Arguments may be integers or floats, and may be positive or negative. Only days, seconds and microseconds are stored internally. 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, is raised. Note that normalization of negative values may be surprising at first. Note that, because of normalization, timedelta. The result is rounded to the nearest multiple of timedelta. The result is rounded to the nearest multiple of timedelta. In the second case, an integer is returned. This leads to somewhat unusual results for negative timedeltas. In addition to the operations listed above objects support certain additions and subtractions with and objects see below. Changed in version 3. True division and multiplication of a object by a object are now supported. Comparisons of objects are supported with the object representing the smaller duration considered to be the smaller timedelta. The latter cases return or , respectively. Note that for very large time intervals greater than 270 years on most platforms this method will lose microsecond accuracy. January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems. Other constructors, all class methods: classmethod date. This is equivalent to date. This may raise , if the timestamp is out of the range of values supported by the platform C localtime function, and on localtime failure. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by. Changed in version 3. Raise instead of on localtime failure. For any date d, date. Specifically, this function supports strings in the format s YYYY-MM-DD. New in version 3. Instance attributes read-only : date. 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. The latter cases return or , respectively. Dates can be used as dictionary keys. In Boolean contexts, all objects are considered to be true. The hours, minutes and seconds are 0, and the DST flag is -1. For any object d, date. For example, date 2002, 12, 4. For example, date 2002, 12, 4. The ISO calendar is a widely used variant of the Gregorian calendar. See for a good explanation. 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, so that date 2003, 12, 29. For example, date 2002, 12, 4. Format codes referring to hours, minutes or seconds will see 0 values. For a complete list of formatting directives, see. This makes it possible to specify a format string for a object in and when using. For a complete list of formatting directives, see. If an argument outside those ranges is given, is raised. New in version 3. Other constructors, all class methods: classmethod datetime. This is equivalent to datetime. If optional argument tz is None or not specified, this is like , but, if possible, supplies more precision than can be gotten from going through a timestamp for example, this may be possible on platforms supplying the C gettimeofday function. In this case the result is equivalent to tz. This is like , but returns the current UTC date and time, as a naive object. An aware current UTC datetime can be obtained by calling datetime. In this case the result is equivalent to tz. Changed in version 3. This may raise , if the timestamp is out of the range of values supported by the platform C gmtime function, and on gmtime failure. To get an aware object, call : Changed in version 3. Raise instead of on gmtime failure. The hour, minute, second and microsecond of the result are all 0, and is None. If the tzinfo argument is provided, its value is used to set the attribute of the result, otherwise the attribute of the time argument is used. If date is a object, its time components and attributes are ignored. Changed in version 3. New in version 3. For a complete list of formatting directives, see. Instance attributes read-only : datetime. 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. New in version 3. Note that no time zone adjustments are done even if the input is an aware object. As for addition, the result has the same attribute as the input datetime, and no time zone adjustments are done even if the input is aware. If one is aware and the other is naive, is raised. No time zone adjustments are done in this case. If both are aware and have different attributes, a-b acts as if a and b were first converted to naive UTC datetimes first. The result is a. If one comparand is naive and the other is aware, 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 attribute, the common attribute is ignored and the base datetimes are compared. If both comparands are aware and have different attributes, the comparands are first adjusted by subtracting their UTC offsets obtained from self. 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. The latter cases return or , respectively. In Boolean contexts, all objects are considered to be true. Changed in version 3. New in version 3. If provided, tz must be an instance of a subclass, and its and methods must not return None. If self is naive, it is presumed to represent time in the system timezone. If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data, use dt. If you merely want to remove the time zone object from an aware datetime dt without conversion of date and time data, use dt. Note that the default method can be overridden in a subclass to affect the result returned by. Ignoring error cases, acts like: Changed in version 3. Changed in version 3. DST is never in effect for a UTC time. If d is aware, d is normalized to UTC time, by subtracting d. Note that an may be raised if d. The same as self. The return value is a similar to that returned by. Naive instances are assumed to represent local time and this method relies on the platform C mktime function to perform the conversion. Since supports wider range of values than mktime on many platforms, this method may raise for times far in the past or far in the future. The same as self. The same as self. The same as self. The optional argument sep default 'T' is a one-character separator, placed between the date and time portions of the result. New in version 3. For a complete list of formatting directives, see. This makes it possible to specify a format string for a object in and when using. For a complete list of formatting directives, see. DST starts last Sunday in March... If an argument outside those ranges is given, is raised. All default to 0 except tzinfo, which defaults to. Instance attributes read-only : time. 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. New in version 3. If one comparand is naive and the other is aware, 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 attribute, the common attribute is ignored and the base times are compared. If both comparands are aware and have different attributes, the comparands are first adjusted by subtracting their UTC offsets obtained from self. The latter cases return or , respectively. Changed in version 3. This behavior was considered obscure and error-prone and has been removed in Python 3. See for full details. Other constructor: classmethod time. New in version 3. New in version 3. The optional argument timespec specifies the number of additional components of the time to include the default is 'auto'. For a complete list of formatting directives, see. This makes it possible to specify a format string for a object in and when using. For a complete list of formatting directives, see. You need to derive a concrete subclass, and at least supply implementations of the standard methods needed by the methods you use. The module supplies a simple concrete subclass of , , which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT. An instance of a concrete subclass of can be passed to the constructors for and objects. The latter objects view their attributes as being in local time, and the 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. Special requirement for pickling: A subclass must have an method that can be called with no arguments, else 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 may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware objects. If in doubt, simply implement all of them. If local time is west of UTC, this should be negative. Note that this is intended to be the total offset from UTC; for example, if a object represents both time zone and DST adjustments, should return their sum. Most implementations of will probably look like one of these two: Changed in version 3. Return timedelta 0 if DST is not in effect. If DST is in effect, return the offset as a object see for details. An instance tz of a subclass that models both standard and daylight times must be consistent in this sense: tz. If a subclass cannot guarantee this, it may be able to override the default implementation of to work correctly with astimezone regardless. Most implementations of will probably look like one of these two: def dst self , dt : Code to set dston and dstoff to the time zone's DST transition times based on the input dt. Changed in version 3. Note that this is a method rather than a fixed string primarily because some subclasses will wish to return different names depending on the specific value of dt passed, especially if the class is accounting for daylight time. The default implementation of raises. These methods are called by a or object, in response to their methods of the same names. A object passes itself as the argument, and a object passes None as the argument. 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. When a object is passed in response to a method, dt. The intent is that the methods interpret dt as being in local time, and not need worry about objects in other timezones. There is one more method that a subclass may wish to override: tzinfo. When called from that, dt. Most subclasses should be able to inherit the default implementation without problems. An example of a time zone the default 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 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 implementation acts like: def fromutc self , dt : raise ValueError error if dt. 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. 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 attribute set to 0 and the later times have it set to 1. See also The standard library has class for handling arbitrary fixed offsets from UTC and as UTC timezone instance. The Time Zone Database often called tz, tzdata or zoneinfo contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules. Objects The class is a subclass of , each instance of which represents a timezone defined by a fixed offset from UTC. Note that 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. The name argument is optional. If specified it must be a string that will be used as the value returned by the method. Changed in version 3. If name is not provided in the constructor, the name returned by tzname dt is generated from the value of the offset as follows. Changed in version 3. The dt argument must be an aware instance, with tzinfo set to self. Conversely, the class method creates a object from a string representing a date and time and a corresponding format string. For objects, the format codes for year, month, and day should not be used, as time objects have no such values. For objects, the format codes for hours, minutes, seconds, and microseconds should not be used, as objects have no such values. To see the full set of format codes supported on your platform, consult the strftime 3 documentation. The following is a list of all the format codes that the C standard 1989 version requires, and these work on all platforms with a standard C implementation. Note that the 1999 version of the C standard added additional format codes. All days in a new year preceding the first Sunday are considered to be in week 0. All days in a new year preceding the first Monday are considered to be in week 0. These parameters all correspond to ISO 8601 date values. These may not be available on all platforms when used with the strftime method. The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling strptime with incomplete or ambiguous ISO 8601 directives will raise a. Directive Meaning Example Notes %G ISO 8601 year with century representing the year that contains the greater part of the ISO week %V. Week 01 is the week containing Jan 4. Changed in version 3. The ffffff part is omitted when the offset is a whole number of seconds and both the ffffff and the SS part is omitted when the offset is a whole number of minutes. Changed in version 3. For example, '+01:00:00' will be parsed as an offset of one hour. In addition, providing 'Z' is identical to '+00:00'. Otherwise %Z is replaced by the returned value, which must be a string. Changed in version 3. The tzinfo of the result will be set to a instance. Also note that %G and %Y are not interchangeable. Footnotes If, that is, we ignore the effects of Relativity.
Python Programming Tutorial - 34: Date & Time functions (Part-2)
The first week of an ISO year is the first Gregorian calendar week of a year containing a Thursday. DST is never in effect for a UTC time. If todays date datetime python argument tz is None or not specified, this is likebut, if possible, supplies more precision than can be gotten from going through a timestamp for example, this may be possible on platforms supplying the C gettimeofday function. The hours, minutes and seconds are 0, and the DST flag is -1. It may be more useful for utcoffset None to return the between UTC offset, as there is no other convention for discovering the standard offset. Also with small changes in the control code in strftime function you can format the style of the text.
