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cpython/Doc/lib/libdatetime.tex
Tim Peters 397301eccb The tzinfo methods utcoffset() and dst() must return a timedelta object 
(or None) now.  In 2.3a1 they could also return an int or long, but that
was an unhelpfully redundant leftover from an earlier version wherein
they couldn't return a timedelta.  TOOWTDI.
2003-01-02 21:28:08 +00:00

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% XXX what order should the types be discussed in?
\section{\module{datetime} ---
Basic date and time types}
\declaremodule{builtin}{datetime}
\modulesynopsis{Basic date and time types.}
\moduleauthor{Tim Peters}{tim@zope.com}
\sectionauthor{Tim Peters}{tim@zope.com}
\sectionauthor{A.M. Kuchling}{amk@amk.ca}
\sectionauthor{Raymond D. Hettinger}{python@rcn.com}
\versionadded{2.3}
The \module{datetime} module supplies classes for manipulating dates
and times in both simple and complex ways. While date and time
arithmetic is supported, the focus of the implementation is on
efficient field extraction, for output formatting and manipulation.
There are two kinds of date and time objects: ``naive'' and ``aware''.
This distinction refers to whether the object has any notion of time
zone, daylight savings time, or other kind of algorithmic or political
time adjustment. Whether a {naive} \class{datetime} object represents
Coordinated Universal Time (UTC), local time, or time in some other
timezone is purely up to the program, just like it's up to the program
whether a particular number represents meters, miles, or mass. Naive
\class{datetime} objects are easy to understand and to work with, at
the cost of ignoring some aspects of reality.
For applications requiring more, ``aware'' \class{datetime} subclasses add an
optional time zone information object to the basic naive classes.
These \class{tzinfo} objects capture information about the offset from
UTC time, the time zone name, and whether Daylight Savings Time is in
effect. Note that no concrete \class{tzinfo} classes are supplied by
the \module{datetime} module. Instead, they provide a framework for
incorporating the level of detail an app may require. The rules for
time adjustment across the world are more political than rational, and
there is no standard suitable for every app.
The \module{datetime} module exports the following constants:
\begin{datadesc}{MINYEAR}
The smallest year number allowed in a \class{date},
\class{datetime}, or \class{datetimetz} object. \constant{MINYEAR}
is \code{1}.
\end{datadesc}
\begin{datadesc}{MAXYEAR}
The largest year number allowed in a \class{date}, \class{datetime},
or \class{datetimetz} object. \constant{MAXYEAR} is \code{9999}.
\end{datadesc}
\begin{seealso}
\seemodule{calendar}{General calendar related functions.}
\seemodule{time}{Time access and conversions.}
\end{seealso}
\subsection{Available Types}
\begin{classdesc*}{date}
An idealized naive date, assuming the current Gregorian calendar
always was, and always will be, in effect.
Attributes: \member{year}, \member{month}, and \member{day}.
\end{classdesc*}
\begin{classdesc*}{time}
An idealized naive 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: \member{hour}, \member{minute}, \member{second}, and
\member{microsecond}
\end{classdesc*}
\begin{classdesc*}{datetime}
A combination of a naive date and a naive time.
Attributes: \member{year}, \member{month}, \member{day},
\member{hour}, \member{minute}, \member{second},
and \member{microsecond}.
\end{classdesc*}
\begin{classdesc*}{timedelta}
A duration, expressing the difference between two \class{date},
\class{time}, or \class{datetime} instances, to microsecond
resolution.
\end{classdesc*}
\begin{classdesc*}{tzinfo}
An abstract base class for time zone information objects. These
are used by the \class{datetimetz} and \class{timetz} classes to
provided a customizable notion of time adjustment (for example, to
account for time zone and/or daylight savings time).
\end{classdesc*}
\begin{classdesc*}{timetz}
An aware subclass of \class{time}, supporting a customizable notion of
time adjustment.
\end{classdesc*}
\begin{classdesc*}{datetimetz}
An aware subclass of \class{datetime}, supporting a customizable notion of
time adjustment.
\end{classdesc*}
Objects of these types are immutable.
Objects of the \class{date}, \class{datetime}, and \class{time} types
are always naive.
An object \var{d} of type \class{timetz} or \class{datetimetz} may be
naive or aware. \var{d} is aware if \code{\var{d}.tzinfo} is not
\code{None}, and \code{\var{d}.tzinfo.utcoffset(\var{d})} does not return
\code{None}. If \code{\var{d}.tzinfo} is \code{None}, or if
\code{\var{d}.tzinfo} is not \code{None} but
\code{\var{d}.tzinfo.utcoffset(\var{d})} returns \code{None}, \var{d}
is naive.
The distinction between naive and aware doesn't apply to
\code{timedelta} objects.
Subclass relationships:
\begin{verbatim}
object
timedelta
tzinfo
time
timetz
date
datetime
datetimetz
\end{verbatim}
\subsection{\class{timedelta} Objects \label{datetime-timedelta}}
A \class{timedelta} object represents a duration, the difference
between two dates or times.
\begin{classdesc}{timedelta}{days=0, seconds=0, microseconds=0,
milliseconds=0, minutes=0, hours=0, weeks=0}
All arguments are optional. Arguments may be ints, longs, or floats,
and may be positive or negative.
Only \var{days}, \var{seconds} and \var{microseconds} are stored
internally. Arguments are converted to those units:
\begin{verbatim}
A millisecond is converted to 1000 microseconds.
A minute is converted to 60 seconds.
An hour is converted to 3600 seconds.
A week is converted to 7 days.
\end{verbatim}
and days, seconds and microseconds are then normalized so that the
representation is unique, with
\begin{itemize}
\item \code{0 <= \var{microseconds} < 1000000}
\item \code{0 <= \var{seconds} < 3600*24} (the number of seconds in one day)
\item \code{-999999999 <= \var{days} <= 999999999}
\end{itemize}
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. 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,
\exception{OverflowError} is raised.
Note that normalization of negative values may be surprising at first.
For example,
\begin{verbatim}
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)
\end{verbatim}
\end{classdesc}
Class attributes are:
\begin{memberdesc}{min}
The most negative \class{timedelta} object,
\code{timedelta(-999999999)}.
\end{memberdesc}
\begin{memberdesc}{max}
The most positive \class{timedelta} object,
\code{timedelta(days=999999999, hours=23, minutes=59, seconds=59,
microseconds=999999)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal
\class{timedelta} objects, \code{timedelta(microseconds=1)}.
\end{memberdesc}
Note that, because of normalization, \code{timedelta.max} \textgreater
\code{-timedelta.min}. \code{-timedelta.max} is not representable as
a \class{timedelta} object.
Instance attributes (read-only):
\begin{tableii}{c|l}{code}{Attribute}{Value}
\lineii{days}{Between -999999999 and 999999999 inclusive}
\lineii{seconds}{Between 0 and 86399 inclusive}
\lineii{microseconds}{Between 0 and 999999 inclusive}
\end{tableii}
Supported operations:
\begin{tableiii}{c|l|c}{code}{Operation}{Result}{Notes}
\lineiii{\var{t1} = \var{t2} + \var{t3}}
{Sum of \var{t2} and \var{t3}.
Afterwards \var{t1}-\var{t2} == \var{t3} and \var{t1}-\var{t3}
== \var{t2} are true.}
{(1)}
\lineiii{\var{t1} = \var{t2} - \var{t3}}
{Difference of \var{t2} and \var{t3}. Afterwards \var{t1} ==
\var{t2} - \var{t3} and \var{t2} == \var{t1} + \var{t3} are
true.}
{(1)}
\lineiii{\var{t1} = \var{t2} * \var{i} or \var{t1} = \var{i} * \var{t2}}
{Delta multiplied by an integer or long.
Afterwards \var{t1} // i == \var{t2} is true,
provided \code{i != 0}.
In general, \var{t1} * i == \var{t1} * (i-1) + \var{t1} is true.}
{(1)}
\lineiii{\var{t1} = \var{t2} // \var{i}}
{The floor is computed and the remainder (if any) is thrown away.}
{(3)}
\lineiii{+\var{t1}}
{Returns a \class{timedelta} object with the same value.}
{(2)}
\lineiii{-\var{t1}}
{equivalent to \class{timedelta}(-\var{t1.days}, -\var{t1.seconds},
-\var{t1.microseconds}),and to \var{t1}* -1.}
{(1)(4)}
\lineiii{abs(\var{t})}
{equivalent to +\var{t} when \code{t.days >= 0}, and to
-\var{t} when \code{t.days < 0}.
overflow.}
{(2)}
\end{tableiii}
\noindent
Notes:
\begin{description}
\item[(1)]
This is exact, but may overflow.
\item[(2)]
This is exact, and cannot overflow.
\item[(3)]
Division by 0 raises \exception{ZeroDivisionError}.
\item[(4)]
-\var{timedelta.max} is not representable as a \class{timedelta} object.
\end{description}
In addition to the operations listed above \class{timedelta} objects
support certain additions and subtractions with \class{date},
\class{datetime}, and \class{datimetz} objects (see below).
Comparisons of \class{timedelta} objects are supported with the
\class{timedelta} object representing the smaller duration considered
to be the smaller timedelta.
\class{timedelta} objects are hashable (usable as dictionary key),
support efficient pickling, and in Boolean contexts, a \class{timedelta}
object is considered to be true if and only if it isn't equal to
\code{timedelta(0)}.
\subsection{\class{date} Objects \label{datetime-date}}
A \class{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. This matches the definition of the
"proleptic Gregorian" calendar in Dershowitz and Reingold's book
\citetitle{Calendrical Calculations}, where it's the base calendar for all
computations. See the book for algorithms for converting between
proleptic Gregorian ordinals and many other calendar systems.
\begin{classdesc}{date}{year, month, day}
All arguments are required. Arguments may be ints or longs, in the
following ranges:
\begin{itemize}
\item \code{MINYEAR <= \var{year} <= MAXYEAR}
\item \code{1 <= \var{month} <= 12}
\item \code{1 <= \var{day} <= number of days in the given month and year}
\end{itemize}
If an argument outside those ranges is given, \exception{ValueError}
is raised.
\end{classdesc}
Other constructors, all class methods:
\begin{methoddesc}{today}{}
Return the current local date. This is equivalent to
\code{date.fromtimestamp(time.time())}.
\end{methoddesc}
\begin{methoddesc}{fromtimestamp}{timestamp}
Return the local date corresponding to the POSIX timestamp, such
as is returned by \function{time.time()}. This may raise
\exception{ValueError}, if the timestamp is out of the range of
values supported by the platform C \cfunction{localtime()}
function. It's common for this to be restricted to years from 1970
through 2038.
\end{methoddesc}
\begin{methoddesc}{fromordinal}{ordinal}
Return the date corresponding to the proleptic Gregorian ordinal,
where January 1 of year 1 has ordinal 1. \exception{ValueError} is
raised unless \code{1 <= \var{ordinal} <= date.max.toordinal()}.
For any date \var{d}, \code{date.fromordinal(\var{d}.toordinal()) ==
\var{d}}.
\end{methoddesc}
Class attributes:
\begin{memberdesc}{min}
The earliest representable date, \code{date(MINYEAR, 1, 1)}.
\end{memberdesc}
\begin{memberdesc}{max}
The latest representable date, \code{date(MAXYEAR, 12, 31)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal date
objects, \code{timedelta(days=1)}.
\end{memberdesc}
Instance attributes (read-only):
\begin{memberdesc}{year}
Between \constant{MINYEAR} and \constant{MAXYEAR} inclusive
\end{memberdesc}
\begin{memberdesc}{month}
Between 1 and 12 inclusive.
\end{memberdesc}
\begin{memberdesc}{day}
Between 1 and the number of days in the given month of the given
year.
\end{memberdesc}
Supported operations:
\begin{itemize}
\item
date1 + timedelta -> date2
timedelta + date1 -> date2
date2 is timedelta.days days removed from the date1, moving forward
in time if timedelta.days > 0, or backward if timedetla.days < 0.
date2 - date1 == timedelta.days after. timedelta.seconds and
timedelta.microseconds are ignored. \exception{OverflowError} is
raised if date2.year would be smaller than \constant{MINYEAR} or
larger than \constant{MAXYEAR}.
\item
date1 - timedelta -> date2
Computes the date2 such that date2 + timedelta == date1. This
isn't quite equivalent to date1 + (-timedelta), because -timedelta
in isolation can overflow in cases where date1 - timedelta does
not. timedelta.seconds and timedelta.microseconds are ignored.
\item
date1 - date2 -> timedelta
This is exact, and cannot overflow. timedelta.seconds and
timedelta.microseconds are 0, and date2 + timedelta == date1
after.
\item
comparison of date to date, where date1 is considered less than
date2 when date1 precedes date2 in time. In other words,
date1 < date2 if and only if date1.toordinal() < date2.toordinal().
\item
hash, use as dict key
\item
efficient pickling
\item
in Boolean contexts, all \class{date} objects are considered to be true
\end{itemize}
Instance methods:
\begin{methoddesc}{replace}{year, month, day}
Return a date with the same value, except for those fields given
new values by whichever keyword arguments are specified. For
example, if \code{d == date(2002, 12, 31)}, then
\code{d.replace(day=26) == date(2000, 12, 26)}.
\end{methoddesc}
\begin{methoddesc}{timetuple}{}
Return a 9-element tuple of the form returned by
\function{time.localtime()}. The hours, minutes and seconds are
0, and the DST flag is -1.
\code{\var{d}.timetuple()} is equivalent to
\code{(\var{d}.year, \var{d}.month, \var{d}.day,
0, 0, 0, \# h, m, s
\var{d}.weekday(), \# 0 is Monday
\var{d}.toordinal() - date(\var{d}.year, 1, 1).toordinal() + 1,
\# day of year
-1)}
\end{methoddesc}
\begin{methoddesc}{toordinal}{}
Return the proleptic Gregorian ordinal of the date, where January 1
of year 1 has ordinal 1. For any \class{date} object \var{d},
\code{date.fromordinal(\var{d}.toordinal()) == \var{d}}.
\end{methoddesc}
\begin{methoddesc}{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 \method{isoweekday()}.
\end{methoddesc}
\begin{methoddesc}{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 \method{weekday()}, \method{isocalendar()}.
\end{methoddesc}
\begin{methoddesc}{isocalendar}{}
Return a 3-tuple, (ISO year, ISO week number, ISO weekday).
The ISO calendar is a widely used variant of the Gregorian calendar.
See \url{http://www.phys.uu.nl/~vgent/calendar/isocalendar.htm}
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).isocalendar() == (2004, 1, 1)
date(2004, 1, 4).isocalendar() == (2004, 1, 7)
\end{methoddesc}
\begin{methoddesc}{isoformat}{}
Return a string representing the date in ISO 8601 format,
'YYYY-MM-DD'. For example,
date(2002, 12, 4).isoformat() == '2002-12-04'.
\end{methoddesc}
\begin{methoddesc}{__str__}{}
For a date \var{d}, \code{str(\var{d})} is equivalent to
\code{\var{d}.isoformat()}.
\end{methoddesc}
\begin{methoddesc}{ctime}{}
Return a string representing the date, for example
date(2002, 12, 4).ctime() == 'Wed Dec 4 00:00:00 2002'.
\code{\var{d}.ctime()} is equivalent to
\code{time.ctime(time.mktime(\var{d}.timetuple()))}
on platforms where the native C \cfunction{ctime()} function
(which \function{time.ctime()} invokes, but which
\method{date.ctime()} does not invoke) conforms to the C standard.
\end{methoddesc}
\begin{methoddesc}{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.
See the section on \method{strftime()} behavior.
\end{methoddesc}
\subsection{\class{datetime} Objects \label{datetime-datetime}}
A \class{datetime} object is a single object containing all the
information from a \class{date} object and a time object. Like a
\class{date} object, \class{datetime} assumes the current Gregorian
calendar extended in both directions; like a time object,
\class{datetime} assumes there are exactly 3600*24 seconds in every
day.
\begin{classdesc}{datetime}{year, month, day,
hour=0, minute=0, second=0, microsecond=0}
The year, month and day arguments are required. Arguments may be
ints or longs, in the following ranges:
\begin{itemize}
\item \code{\member{MINYEAR} <= \var{year} <= \member{MAXYEAR}}
\item \code{1 <= \var{month} <= 12}
\item \code{1 <= \var{day} <= number of days in the given month and year}
\item \code{0 <= \var{hour} < 24}
\item \code{0 <= \var{minute} < 60}
\item \code{0 <= \var{second} < 60}
\item \code{0 <= \var{microsecond} < 1000000}
\end{itemize}
If an argument outside those ranges is given, \exception{ValueError}
is raised.
\end{classdesc}
Other constructors, all class methods:
\begin{methoddesc}{today}{}
Return the current local datetime. This is equivalent to
\code{datetime.fromtimestamp(time.time())}.
See also \method{now()}, \method{fromtimestamp()}.
\end{methoddesc}
\begin{methoddesc}{now}{}
Return the current local datetime. This is like \method{today()},
but, if possible, supplies more precision than can be gotten from
going through a \function{time.time()} timestamp (for example,
this may be possible on platforms that supply the C
\cfunction{gettimeofday()} function).
See also \method{today()}, \method{utcnow()}.
\end{methoddesc}
\begin{methoddesc}{utcnow}{}
Return the current UTC datetime. This is like \method{now()}, but
returns the current UTC date and time.
See also \method{now()}.
\end{methoddesc}
\begin{methoddesc}{fromtimestamp}{timestamp}
Return the local \class{datetime} corresponding to the \POSIX{}
timestamp, such as is returned by \function{time.time()}. This
may raise \exception{ValueError}, if the timestamp is out of the
range of values supported by the platform C
\cfunction{localtime()} function. It's common for this to be
restricted to years in 1970 through 2038.
See also \method{utcfromtimestamp()}.
\end{methoddesc}
\begin{methoddesc}{utcfromtimestamp}{timestamp}
Return the UTC \class{datetime} corresponding to the \POSIX{}
timestamp. This may raise \exception{ValueError}, if the
timestamp is out of the range of values supported by the platform
C \cfunction{gmtime()} function. It's common for this to be
restricted to years in 1970 through 2038.
See also \method{fromtimestamp()}.
\end{methoddesc}
\begin{methoddesc}{fromordinal}{ordinal}
Return the \class{datetime} corresponding to the proleptic
Gregorian ordinal, where January 1 of year 1 has ordinal 1.
\exception{ValueError} is raised unless 1 <= ordinal <=
datetime.max.toordinal(). The hour, minute, second and
microsecond of the result are all 0.
\end{methoddesc}
\begin{methoddesc}{combine}{date, time}
Return a new \class{datetime} object whose date components are
equal to the given \class{date} object's, and whose time
components are equal to the given time object's. For any
\class{datetime} object \var{d}, \code{\var{d} ==
datetime.combine(\var{d}.date(), \var{d}.time())}. If date is a
\class{datetime} or \class{datetimetz} object, its time components
are ignored. If date is \class{datetimetz} object, its
\member{tzinfo} component is also ignored. If time is a
\class{timetz} object, its \member{tzinfo} component is ignored.
\end{methoddesc}
Class attributes:
\begin{memberdesc}{min}
The earliest representable \class{datetime},
\code{datetime(MINYEAR, 1, 1)}.
\end{memberdesc}
\begin{memberdesc}{max}
The latest representable \class{datetime},
\code{datetime(MAXYEAR, 12, 31, 23, 59, 59, 999999)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal \class{datetime}
objects, \code{timedelta(microseconds=1)}.
\end{memberdesc}
Instance attributes (read-only):
\begin{memberdesc}{year}
Between \constant{MINYEAR} and \constant{MAXYEAR} inclusive
\end{memberdesc}
\begin{memberdesc}{month}
Between 1 and 12 inclusive
\end{memberdesc}
\begin{memberdesc}{day}
Between 1 and the number of days in the given month of the given
year.
\end{memberdesc}
\begin{memberdesc}{hour}
In \code{range(24)}.
\end{memberdesc}
\begin{memberdesc}{minute}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{second}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{microsecond}
In \code{range(1000000)}.
\end{memberdesc}
Supported operations:
\begin{itemize}
\item
datetime1 + timedelta -> datetime2
timedelta + datetime1 -> datetime2
datetime2 is a duration of timedelta removed from datetime1, moving
forward in time if timedelta.days > 0, or backward if
timedelta.days < 0. datetime2 - datetime1 == timedelta after.
\exception{OverflowError} is raised if datetime2.year would be
smaller than \constant{MINYEAR} or larger than \constant{MAXYEAR}.
\item
datetime1 - timedelta -> datetime2
Computes the datetime2 such that datetime2 + timedelta == datetime1.
This isn't quite equivalent to datetime1 + (-timedelta), because
-timedelta in isolation can overflow in cases where
datetime1 - timedelta does not.
\item
datetime1 - datetime2 -> timedelta
This is exact, and cannot overflow.
datetime2 + timedelta == datetime1 after.
\item
comparison of \class{datetime} to datetime, where datetime1 is
considered less than datetime2 when datetime1 precedes datetime2
in time.
\item
hash, use as dict key
\item
efficient pickling
\item
in Boolean contexts, all \class{datetime} objects are considered
to be true
\end{itemize}
Instance methods:
\begin{methoddesc}{date}{}
Return \class{date} object with same year, month and day.
\end{methoddesc}
\begin{methoddesc}{time}{}
Return time object with same hour, minute, second and microsecond.
\end{methoddesc}
\begin{methoddesc}{replace}{year=, month=, day=, hour=, minute=,
second=, microsecond=}
Return a datetime with the same value, except for those fields given
new values by whichever keyword arguments are specified.
\end{methoddesc}
\begin{methoddesc}{astimezone}{tz}
Return a \class{datetimetz} with the same date and time fields, and
with \member{tzinfo} member \var{tz}. \var{tz} must be \code{None},
or an instance of a \class{tzinfo} subclass.
\end{methoddesc}
\begin{methoddesc}{timetuple}{}
Return a 9-element tuple of the form returned by
\function{time.localtime()}.
The DST flag is -1. \code{\var{d}.timetuple()} is equivalent to
\code{(\var{d}.year, \var{d}.month, \var{d}.day,
\var{d}.hour, \var{d}.minute, \var{d}.second,
\var{d}.weekday(), \# 0 is Monday
\var{d}.toordinal() - date(\var{d}.year, 1, 1).toordinal() + 1,
\# day of year
-1)}
\end{methoddesc}
\begin{methoddesc}{toordinal}{}
Return the proleptic Gregorian ordinal of the date. The same as
\method{date.toordinal()}.
\end{methoddesc}
\begin{methoddesc}{weekday}{}
Return the day of the week as an integer, where Monday is 0 and
Sunday is 6. The same as \method{date.weekday()}.
See also \method{isoweekday()}.
\end{methoddesc}
\begin{methoddesc}{isoweekday}{}
Return the day of the week as an integer, where Monday is 1 and
Sunday is 7. The same as \method{date.isoweekday()}.
See also \method{weekday()}, \method{isocalendar()}.
\end{methoddesc}
\begin{methoddesc}{isocalendar}{}
Return a 3-tuple, (ISO year, ISO week number, ISO weekday). The
same as \method{date.isocalendar()}.
\end{methoddesc}
\begin{methoddesc}{isoformat}{sep='T'}
Return a string representing the date and time in ISO 8601 format,
YYYY-MM-DDTHH:MM:SS.mmmmmm
or, if self.microsecond is 0,
YYYY-MM-DDTHH:MM:SS
The optional argument \var{sep} (default \code{'T'}) is a
one-character separator, placed between the date and time portions
of the result. For example,
datetime(2002, 12, 4, 1, 2, 3, 4).isoformat(' ') ==
'2002-12-04 01:02:03.000004'
\end{methoddesc}
\begin{methoddesc}{__str__}{}
For a \class{datetime} instance \var{d}, \code{str(\var{d})} is
equivalent to \code{\var{d}.isoformat(' ')}.
\end{methoddesc}
\begin{methoddesc}{ctime}{}
Return a string representing the date, for example
datetime(2002, 12, 4, 20, 30, 40).ctime() == 'Wed Dec 4 20:30:40 2002'.
\code{d.ctime()} is equivalent to
\code{time.ctime(time.mktime(d.timetuple()))} on platforms where
the native C \cfunction{ctime()} function (which
\function{time.ctime()} invokes, but which
\method{datetime.ctime()} does not invoke) conforms to the C
standard.
\end{methoddesc}
\begin{methoddesc}{strftime}{format}
Return a string representing the date and time, controlled by an
explicit format string. See the section on \method{strftime()}
behavior.
\end{methoddesc}
\subsection{\class{time} Objects \label{datetime-time}}
A \class{time} object represents an idealized time of day, independent
of day and timezone.
\begin{classdesc}{time}{hour=0, minute=0, second=0, microsecond=0}
All arguments are optional. They may be ints or longs, in the
following ranges:
\begin{itemize}
\item \code{0 <= \var{hour} < 24}
\item \code{0 <= \var{minute} < 60}
\item \code{0 <= \var{second} < 60}
\item \code{0 <= \var{microsecond} < 1000000}
\end{itemize}
If an argument outside those ranges is given, \exception{ValueError}
is raised.
\end{classdesc}
Class attributes:
\begin{memberdesc}{min}
The earliest representable \class{time}, \code{time(0, 0, 0, 0)}.
\end{memberdesc}
\begin{memberdesc}{max}
The latest representable \class{time}, \code{time(23, 59, 59, 999999)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal \class{time}
objects, \code{timedelta(microseconds=1)}, although note that
arithmetic on \class{time} objects is not supported.
\end{memberdesc}
Instance attributes (read-only):
\begin{memberdesc}{hour}
In \code{range(24)}.
\end{memberdesc}
\begin{memberdesc}{minute}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{second}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{microsecond}
In \code{range(1000000)}.
\end{memberdesc}
Supported operations:
\begin{itemize}
\item
comparison of time to time, where time1 is considered
less than time2 when time1 precedes time2 in time.
\item
hash, use as dict key
\item
efficient pickling
\item
in Boolean contexts, a time object is considered to be true
if and only if it isn't equal to \code{time(0)}
\end{itemize}
Instance methods:
\begin{methoddesc}{replace}{hour=, minute=, second=, microsecond=}
Return a time with the same value, except for those fields given
new values by whichever keyword arguments are specified.
\end{methoddesc}
\begin{methoddesc}{isoformat}{}
Return a string representing the time in ISO 8601 format,
HH:MM:SS.mmmmmm
or, if self.microsecond is 0
HH:MM:SS
\end{methoddesc}
\begin{methoddesc}{__str__}{}
For a time \var{t}, \code{str(\var{t})} is equivalent to
\code{\var{t}.isoformat()}.
\end{methoddesc}
\begin{methoddesc}{strftime}{format}
Return a string representing the time, controlled by an explicit
format string. See the section on \method{strftime()} behavior.
\end{methoddesc}
\subsection{\class{tzinfo} Objects \label{datetime-tzinfo}}
\class{tzinfo} is an abstract base clase, meaning that this class
should not be instantiated directly. You need to derive a concrete
subclass, and (at least) supply implementations of the standard
\class{tzinfo} methods needed by the \class{datetime} methods you
use. The \module{datetime} module does not supply any concrete
subclasses of \class{tzinfo}.
An instance of (a concrete subclass of) \class{tzinfo} can be passed
to the constructors for \class{datetimetz} and \class{timetz} objects.
The latter objects view their fields as being in local time, and the
\class{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.
Special requirement for pickling: A \class{tzinfo} subclass must have an
\method{__init__} 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 \class{tzinfo} may need to implement the
following methods. Exactly which methods are needed depends on the
uses made of aware \module{datetime} objects. If in doubt, simply
implement all of them.
\begin{methoddesc}{utcoffset}{self, dt}
Return offset of local time from UTC, in minutes east of UTC. 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
\class{tzinfo} object represents both time zone and DST adjustments,
\method{utcoffset()} should return their sum. If the UTC offset
isn't known, return \code{None}. Else the value returned must be
a \class{timedelta} object specifying a whole number of minutes in the
range -1439 to 1439 inclusive (1440 = 24*60; the magnitude of the offset
must be less than one day). Most implementations of
\method{utcoffset()} will probably look like one of these two:
\begin{verbatim}
return CONSTANT # fixed-offset class
return CONSTANT + self.dst(dt) # daylight-aware class
\end{verbatim}
If \method{utcoffset()} does not return \code{None},
\method{dst()} should not return \code{None} either.
\end{methoddesc}
\begin{methoddesc}{dst}{self, dt}
Return the daylight savings time (DST) adjustment, in minutes east of
UTC, or \code{None} if DST information isn't known. Return \code{0} if
DST is not in effect.
If DST is in effect, return the offset as a
\class{timedelta} object (see \method{utcoffset()} for details).
Note that DST offset, if applicable, has
already been added to the UTC offset returned by
\method{utcoffset()}, so there's no need to consult \method{dst()}
unless you're interested in displaying DST info separately. For
example, \method{datetimetz.timetuple()} calls its \member{tzinfo}
member's \method{dst()} method to determine how the
\member{tm_isdst} flag should be set, and
\method{datetimetz.astimezone()} calls \method{dst()} to account for
DST changes when crossing time zones.
An instance \var{tz} of a \class{tzinfo} subclass that models both
standard and daylight times must be consistent in this sense:
\code{tz.utcoffset(dt) - tz.dst(dt)}
must return the same result for every \class{datetimetz} \var{dt}
in a given year with \code{dt.tzinfo==tz} For sane \class{tzinfo}
subclasses, this expression yields the time zone's "standard offset"
within the year, which should be the same across all days in the year.
The implementation of \method{datetimetz.astimezone()} relies on this,
but cannot detect violations; it's the programmer's responsibility to
ensure it.
\begin{methoddesc}{tzname}{self, dt}
Return the timezone name corresponding to the \class{datetime} represented
by \var{dt}, as a string. Nothing about string names is defined by the
\module{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
\code{None} if a string name isn't known. Note that this is a method
rather than a fixed string primarily because some \class{tzinfo} objects
will wish to return different names depending on the specific value
of \var{dt} passed, especially if the \class{tzinfo} class is
accounting for daylight time.
\end{methoddesc}
\end{methoddesc}
These methods are called by a \class{datetimetz} or \class{timetz} object,
in response to their methods of the same names. A \class{datetimetz}
object passes itself as the argument, and a \class{timetz} object passes
\code{None} as the argument. A \class{tzinfo} subclass's methods should
therefore be prepared to accept a \var{dt} argument of \code{None}, or of
class \class{datetimetz}.
When \code{None} is passed, it's up to the class designer to decide the
best response. For example, returning \code{None} is appropriate if the
class wishes to say that timetz objects don't participate in the
\class{tzinfo} protocol. In other applications, it may be more useful
for \code{utcoffset(None)} to return the standard UTC offset.
When a \class{datetimetz} object is passed in response to a
\class{datetimetz} method, \code{dt.tzinfo} is the same object as
\var{self}. \class{tzinfo} methods can rely on this, unless
user code calls \class{tzinfo} methods directly. The intent is that
the \class{tzinfo} methods interpret \var{dt} as being in local time,
and not need to worry about objects in other timezones.
Example \class{tzinfo} classes:
\verbatiminput{tzinfo-examples.py}
\subsection{\class{timetz} Objects \label{datetime-timetz}}
A time object represents a (local) time of day, independent of any
particular day, and subject to adjustment via a \class{tzinfo} object.
Constructor:
\begin{classdesc}{time}{hour=0, minute=0, second=0, microsecond=0,
tzinfo=None}
All arguments are optional. \var{tzinfo} may be \code{None}, or
an instance of a \class{tzinfo} subclass. The remaining arguments
may be ints or longs, in the following ranges:
\begin{itemize}
\item \code{0 <= \var{hour} < 24}
\item \code{0 <= \var{minute} < 60}
\item \code{0 <= \var{second} < 60}
\item \code{0 <= \var{microsecond} < 1000000}.
\end{itemize}
If an argument outside those ranges is given,
\exception{ValueError} is raised.
\end{classdesc}
Class attributes:
\begin{memberdesc}{min}
The earliest representable time, \code{timetz(0, 0, 0, 0)}.
\end{memberdesc}
\begin{memberdesc}{max}
The latest representable time, \code{timetz(23, 59, 59, 999999)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal \class{timetz}
objects, \code{timedelta(microseconds=1)}, although note that
arithmetic on \class{timetz} objects is not supported.
\end{memberdesc}
Instance attributes (read-only):
\begin{memberdesc}{hour}
In \code{range(24)}.
\end{memberdesc}
\begin{memberdesc}{minute}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{second}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{microsecond}
In \code{range(1000000)}.
\end{memberdesc}
\begin{memberdesc}{tzinfo}
The object passed as the tzinfo argument to the \class{timetz}
constructor, or \code{None} if none was passed.
\end{memberdesc}
Supported operations:
\begin{itemize}
\item
comparison of \class{timetz} to \class{time} or \class{timetz},
where \var{a} is considered less than \var{b} when \var{a} precedes
\var{b} in time. If one comparand is naive and the other is aware,
\exception{TypeError} is raised. If both comparands are aware, and
have the same \member{tzinfo} member, the common \member{tzinfo}
member is ignored and the base times are compared. If both
comparands are aware and have different \member{tzinfo} members,
the comparands are first adjusted by subtracting their UTC offsets
(obtained from \code{self.utcoffset()}).
\item
hash, use as dict key
\item
pickling
\item
in Boolean contexts, a \class{timetz} object is considered to be
true if and only if, after converting it to minutes and
subtracting \method{utcoffset()} (or \code{0} if that's
\code{None}), the result is non-zero.
\end{itemize}
Instance methods:
\begin{methoddesc}{replace}(hour=, minute=, second=, microsecond=, tzinfo=)
Return a \class{timetz} with the same value, except for those fields given
new values by whichever keyword arguments are specified. Note that
\code{tzinfo=None} can be specified to create a naive \class{timetz} from an
aware \class{timetz}.
\end{methoddesc}
\begin{methoddesc}{isoformat}{}
Return a string representing the time in ISO 8601 format,
HH:MM:SS.mmmmmm
or, if self.microsecond is 0,
HH:MM:SS
If \method{utcoffset()} does not return \code{None}, a 6-character
string is appended, giving the UTC offset in (signed) hours and
minutes:
HH:MM:SS.mmmmmm+HH:MM
or, if self.microsecond is 0,
HH:MM:SS+HH:MM
\end{methoddesc}
\begin{methoddesc}{__str__}{}
For a \class{timetz} \var{t}, \code{str(\var{t})} is equivalent to
\code{\var{t}.isoformat()}.
\end{methoddesc}
\begin{methoddesc}{strftime}{format}
Return a string representing the time, controlled by an explicit
format string. See the section on \method{strftime()} behavior.
\end{methoddesc}
\begin{methoddesc}{utcoffset}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
\code{tzinfo.utcoffset(self)} converted to a \class{timedelta}
object.
\end{methoddesc}
\begin{methoddesc}{tzname}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
\code{tzinfo.tzname(self)}.
\end{methoddesc}
\begin{methoddesc}{dst}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
\code{tzinfo.dst(self)} converted to a \class{timedelta} object.
\end{methoddesc}
\subsection{ \class{datetimetz} Objects \label{datetime-datetimetz}}
\begin{notice}[warning]
I think this is \emph{still} missing some methods from the
Python implementation.
\end{notice}
A \class{datetimetz} object is a single object containing all the information
from a \class{date} object and a \class{timetz} object.
Constructor:
\begin{classdesc}{datetimetz}{year, month, day,
hour=0, minute=0, second=0, microsecond=0,
tzinfo=None}
The year, month and day arguments are required. \var{tzinfo} may
be \code{None}, or an instance of a \class{tzinfo} subclass. The
remaining arguments may be ints or longs, in the following ranges:
\begin{itemize}
\item \code{MINYEAR <= \var{year} <= MAXYEAR}
\item \code{1 <= \var{month} <= 12}
\item \code{1 <= \var{day} <= number of days in the given month and year}
\item \code{0 <= \var{hour} < 24}
\item \code{0 <= \var{minute} < 60}
\item \code{0 <= \var{second} < 60}
\item \code{0 <= \var{microsecond} < 1000000}
\end{itemize}
If an argument outside those ranges is given,
\exception{ValueError} is raised.
\end{classdesc}
Other constructors (class methods):
\begin{funcdesc}{today}{}
\methodline{utcnow}{}
\methodline{utcfromtimestamp}{timestamp}
\methodline{fromordinal}{ordinal}
These are the same as the \class{datetime} class methods of the
same names, except that they construct a \class{datetimetz}
object, with tzinfo \code{None}.
\end{funcdesc}
\begin{funcdesc}{now}{\optional{tzinfo=None}}
\methodline{fromtimestamp}{timestamp\optional{, tzinfo=None}}
These are the same as the \class{datetime} class methods of the
same names, except that they accept an additional, optional tzinfo
argument, and construct a \class{datetimetz} object with that
\class{tzinfo} object attached.
\end{funcdesc}
\begin{funcdesc}{combine}{date, time}
This is the same as \method{datetime.combine()}, except that it
constructs a \class{datetimetz} object, and, if the time object is
of type timetz, the \class{datetimetz} object has the same
\class{tzinfo} object as the time object.
\end{funcdesc}
Class attributes:
\begin{memberdesc}{min}
The earliest representable \class{datetimetz},
\code{datetimetz(MINYEAR, 1, 1)}.
\end{memberdesc}
\begin{memberdesc}{max}
The latest representable \class{datetime},
\code{datetimetz(MAXYEAR, 12, 31, 23, 59, 59, 999999)}.
\end{memberdesc}
\begin{memberdesc}{resolution}
The smallest possible difference between non-equal \class{datetimetz}
objects, \code{timedelta(microseconds=1)}.
\end{memberdesc}
Instance attributes, all read-only:
\begin{memberdesc}{year}
Between \constant{MINYEAR} and \constant{MAXYEAR}, inclusive.
\end{memberdesc}
\begin{memberdesc}{month}
Between 1 and 12 inclusive
\end{memberdesc}
\begin{memberdesc}{day}
Between 1 and the number of days in the given month of the given
year.
\end{memberdesc}
\begin{memberdesc}{hour}
In \code{range(24)}.
\end{memberdesc}
\begin{memberdesc}{minute}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{second}
In \code{range(60)}.
\end{memberdesc}
\begin{memberdesc}{microsecond}
In \code{range(1000000)}.
\end{memberdesc}
\begin{memberdesc}{tzinfo}
The object passed as the \var{tzinfo} argument to the
\class{datetimetz} constructor, or \code{None} if none was passed.
\end{memberdesc}
Supported operations:
\begin{itemize}
\item
datetimetz1 + timedelta -> datetimetz2
timedelta + datetimetz1 -> datetimetz2
The same as addition of \class{datetime} objects, except that
datetimetz2.tzinfo is set to datetimetz1.tzinfo.
\item
datetimetz1 - timedelta -> datetimetz2
The same as addition of \class{datetime} objects, except that
datetimetz2.tzinfo is set to datetimetz1.tzinfo.
\item
aware_datetimetz1 - aware_datetimetz2 -> timedelta
naive_datetimetz1 - naive_datetimetz2 -> timedelta
naive_datetimetz1 - datetime2 -> timedelta
datetime1 - naive_datetimetz2 -> timedelta
Subtraction of a \class{datetime} or \class{datetimetz}, from a
\class{datetime} or \class{datetimetz}, is defined only if both
operands are naive, or if both are aware. If one is aware and the
other is naive, \exception{TypeError} is raised.
If both are naive, or both are aware and have the same \member{tzinfo}
member, subtraction acts as for \class{datetime} subtraction.
If both are aware and have different \member{tzinfo} members,
\code{a-b} acts as if \var{a} and \var{b} were first converted to UTC
datetimes (by subtracting \code{a.utcoffset()} minutes from \var{a},
and \code{b.utcoffset()} minutes from \var{b}), and then doing
\class{datetime} subtraction, except that the implementation never
overflows.
\item
comparison of \class{datetimetz} to \class{datetime} or
\class{datetimetz}, where \var{a} is considered less than \var{b}
when \var{a} precedes \var{b} in time. If one comparand is naive and
the other is aware, \exception{TypeError} is raised. If both
comparands are aware, and have the same \member{tzinfo} member,
the common \member{tzinfo} member is ignored and the base datetimes
are compared. If both comparands are aware and have different
\member{tzinfo} members, the comparands are first adjusted by
subtracting their UTC offsets (obtained from \code{self.utcoffset()}).
\item
hash, use as dict key
\item
efficient pickling
\item
in Boolean contexts, all \class{datetimetz} objects are considered to be
true
\end{itemize}
Instance methods:
\begin{methoddesc}{date}{}
\methodline{time}{}
\methodline{toordinal}{}
\methodline{weekday}{}
\methodline{isoweekday}{}
\methodline{isocalendar}{}
\methodline{ctime}{}
\methodline{__str__}{}
\methodline{strftime}{format}
These are the same as the \class{datetime} methods of the same names.
\end{methoddesc}
\begin{methoddesc}{timetz}{}
Return \class{timetz} object with same hour, minute, second, microsecond,
and tzinfo.
\end{methoddesc}
\begin{methoddesc}{replace}{year=, month=, day=, hour=, minute=, second=,
microsecond=, tzinfo=}
Return a datetimetz with the same value, except for those fields given
new values by whichever keyword arguments are specified. Note that
\code{tzinfo=None} can be specified to create a naive datetimetz from
an aware datetimetz.
\end{methoddesc}
\begin{methoddesc}{astimezone}{tz}
Return a \class{datetimetz} with new tzinfo member \var{tz}. \var{tz}
must be \code{None}, or an instance of a \class{tzinfo} subclass. If
\var{tz} is \code{None}, self is naive, or
\code{tz.utcoffset(self)} returns \code{None},
\code{self.astimezone(tz)} is equivalent to
\code{self.replace(tzinfo=tz)}: a new timezone object is attached
without any conversion of date or time fields. If self is aware and
\code{tz.utcoffset(self)} does not return \code{None}, the date and
time fields are adjusted so that the result is local time in timezone
tz, representing the same UTC time as self.
XXX [The treatment of endcases remains unclear: for DST-aware
classes, one hour per year has two spellings in local time, and
another hour has no spelling in local time.] XXX
\end{methoddesc}
\begin{methoddesc}{utcoffset}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
\code{tzinfo.utcoffset(self)} converted to a \class{timedelta}
object.
\end{methoddesc}
\begin{methoddesc}{tzname}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
returns \code{tzinfo.tzname(self)}.
\end{methoddesc}
\begin{methoddesc}{dst}{}
If \member{tzinfo} is \code{None}, returns \code{None}, else
\code{tzinfo.dst(self)} converted to a \class{timedelta}
object.
\end{methoddesc}
\begin{methoddesc}{timetuple}{}
Like \function{datetime.timetuple()}, but sets the
\member{tm_isdst} flag according to the \method{dst()} method: if
\method{dst()} returns \code{None}, \member{tm_isdst} is set to
\code{-1}; else if \method{dst()} returns a non-zero value,
\member{tm_isdst} is set to \code{1}; else \code{tm_isdst} is set
to \code{0}.
\end{methoddesc}
\begin{methoddesc}{utctimetuple}{}
If \class{datetimetz} instance \var{d} is naive, this is the same as
\code{\var{d}.timetuple()} except that \member{tm_isdst} is forced to 0
regardless of what \code{d.dst()} returns. DST is never in effect
for a UTC time.
If \var{d} is aware, \var{d} is normalized to UTC time, by subtracting
\code{\var{d}.utcoffset()} minutes, and a timetuple for the
normalized time is returned. \member{tm_isdst} is forced to 0.
Note that the result's \member{tm_year} field may be
\constant{MINYEAR}-1 or \constant{MAXYEAR}+1, if \var{d}.year was
\code{MINYEAR} or \code{MAXYEAR} and UTC adjustment spills over a
year boundary.
\end{methoddesc}
\begin{methoddesc}{isoformat}{sep='T'}
Return a string representing the date and time in ISO 8601 format,
YYYY-MM-DDTHH:MM:SS.mmmmmm
or, if \member{microsecond} is 0,
YYYY-MM-DDTHH:MM:SS
If \method{utcoffset()} does not return \code{None}, a 6-character
string is appended, giving the UTC offset in (signed) hours and
minutes:
YYYY-MM-DDTHH:MM:SS.mmmmmm+HH:MM
or, if \member{microsecond} is 0
YYYY-MM-DDTHH:MM:SS+HH:MM
The optional argument \var{sep} (default \code{'T'}) is a
one-character separator, placed between the date and time portions
of the result. For example,
\begin{verbatim}
>>> from datetime import *
>>> class TZ(tzinfo):
... def utcoffset(self, dt): return timedelta(minutes=-399)
...
>>> datetimetz(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
\end{verbatim}
\end{methoddesc}
\code{str(\var{d})} is equivalent to \code{\var{d}.isoformat(' ')}.
\subsection{\method{strftime()} Behavior}
\class{date}, \class{datetime}, \class{datetimetz}, \class{time},
and \class{timetz} objects all support a \code{strftime(\var{format})}
method, to create a string representing the time under the control of
an explicit format string. Broadly speaking,
\code{d.strftime(fmt)}
acts like the \refmodule{time} module's
\code{time.strftime(fmt, d.timetuple())}
although not all objects support a \method{timetuple()} method.
For \class{time} and \class{timetz} objects, the format codes for
year, month, and day should not be used, as time objects have no such
values. If they're used anyway, \code{1900} is substituted for the
year, and \code{0} for the month and day.
For \class{date} objects, the format codes for hours, minutes, and
seconds should not be used, as \class{date} objects have no such
values. If they're used anyway, \code{0} is substituted for them.
For a naive object, the \code{\%z} and \code{\%Z} format codes are
replaced by empty strings.
For an aware object:
\begin{itemize}
\item[\code{\%z}]
\method{utcoffset()} is transformed into a 5-character string of
the form +HHMM or -HHMM, where HH is a 2-digit string giving the
number of UTC offset hours, and MM is a 2-digit string giving the
number of UTC offset minutes. For example, if
\method{utcoffset()} returns \code{timedelta(hours=-3, minutes=-30)},
\code{\%z} is replaced with the string \code{'-0330'}.
\item[\code{\%Z}]
If \method{tzname()} returns \code{None}, \code{\%Z} is replaced
by an empty string. Otherwise \code{\%Z} is replaced by the returned
value, which must be a string.
\end{itemize}
The full set of format codes supported varies across platforms,
because Python calls the platform C library's \function{strftime()}
function, and platform variations are common. The documentation for
Python's \refmodule{time} module lists the format codes that the C
standard (1989 version) requires, and those work on all platforms
with a standard C implementation. Note that the 1999 version of the
C standard added additional format codes.
The exact range of years for which \method{strftime()} works also
varies across platforms. Regardless of platform, years before 1900
cannot be used.
\begin{comment}
\subsection{C API}
Struct typedefs:
PyDateTime_Date
PyDateTime_DateTime
PyDateTime_DateTimeTZ
PyDateTime_Time
PyDateTime_TimeTZ
PyDateTime_Delta
PyDateTime_TZInfo
Type-check macros:
PyDate_Check(op)
PyDate_CheckExact(op)
PyDateTime_Check(op)
PyDateTime_CheckExact(op)
PyDateTimeTZ_Check(op)
PyDateTimeTZ_CheckExact(op)
PyTime_Check(op)
PyTime_CheckExact(op)
PyTimeTZ_Check(op)
PyTimeTZ_CheckExact(op)
PyDelta_Check(op)
PyDelta_CheckExact(op)
PyTZInfo_Check(op)
PyTZInfo_CheckExact(op)
Accessor macros:
All objects are immutable, so accessors are read-only. All macros
return ints:
For \class{date}, \class{datetime}, and \class{datetimetz} instances:
PyDateTime_GET_YEAR(o)
PyDateTime_GET_MONTH(o)
PyDateTime_GET_DAY(o)
For \class{datetime} and \class{datetimetz} instances:
PyDateTime_DATE_GET_HOUR(o)
PyDateTime_DATE_GET_MINUTE(o)
PyDateTime_DATE_GET_SECOND(o)
PyDateTime_DATE_GET_MICROSECOND(o)
For \class{time} and \class{timetz} instances:
PyDateTime_TIME_GET_HOUR(o)
PyDateTime_TIME_GET_MINUTE(o)
PyDateTime_TIME_GET_SECOND(o)
PyDateTime_TIME_GET_MICROSECOND(o)
\end{comment}
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