6.9 time -- Time access and conversions

This module provides various time-related functions. It is always available, but not all functions are available on all platforms.

An explanation of some terminology and conventions is in order.

The module defines the following functions and data items:

accept2dyear
Boolean value indicating whether two-digit year values will be accepted. This is true by default, but will be set to false if the environment variable PYTHONY2K has been set to a non-empty string. It may also be modified at run time.

altzone
The offset of the local DST timezone, in seconds west of UTC, if one is defined. This is negative if the local DST timezone is east of UTC (as in Western Europe, including the UK). Only use this if daylight is nonzero.

asctime([tuple])
Convert a tuple representing a time as returned by gmtime() or localtime() to a 24-character string of the following form: 'Sun Jun 20 23:21:05 1993'. If tuple is not provided, the current time as returned by localtime() is used. Note: Unlike the C function of the same name, there is no trailing newline. Changed in version 2.1: Allowed tuple to be omitted.

clock()
On Unix, return the current processor time as a floating point number expressed in seconds. The precision, and in fact the very definition of the meaning of ``processor time'' , depends on that of the C function of the same name, but in any case, this is the function to use for benchmarking Python or timing algorithms.

On Windows, this function returns wall-clock seconds elapsed since the first call to this function, as a floating point number, based on the Win32 function QueryPerformanceCounter(). The resolution is typically better than one microsecond.

ctime([secs])
Convert a time expressed in seconds since the epoch to a string representing local time. If secs is not provided, the current time as returned by time() is used. ctime(secs) is equivalent to asctime(localtime(secs)). Changed in version 2.1: Allowed secs to be omitted.

daylight
Nonzero if a DST timezone is defined.

gmtime([secs])
Convert a time expressed in seconds since the epoch to a time tuple in UTC in which the dst flag is always zero. If secs is not provided, the current time as returned by time() is used. Fractions of a second are ignored. See above for a description of the tuple lay-out. Changed in version 2.1: Allowed secs to be omitted.

localtime([secs])
Like gmtime() but converts to local time. The dst flag is set to 1 when DST applies to the given time. Changed in version 2.1: Allowed secs to be omitted.

mktime(tuple)
This is the inverse function of localtime(). Its argument is the full 9-tuple (since the dst flag is needed; use -1 as the dst flag if it is unknown) which expresses the time in local time, not UTC. It returns a floating point number, for compatibility with time(). If the input value cannot be represented as a valid time, either OverflowError or ValueError will be raised (which depends on whether the invalid value is caught by Python or the underlying C libraries). The earliest date for which it can generate a time is platform-dependent.

sleep(secs)
Suspend execution for the given number of seconds. The argument may be a floating point number to indicate a more precise sleep time. The actual suspension time may be less than that requested because any caught signal will terminate the sleep() following execution of that signal's catching routine. Also, the suspension time may be longer than requested by an arbitrary amount because of the scheduling of other activity in the system.

strftime(format[, tuple])
Convert a tuple representing a time as returned by gmtime() or localtime() to a string as specified by the format argument. If tuple is not provided, the current time as returned by localtime() is used. format must be a string. Changed in version 2.1: Allowed tuple to be omitted.

The following directives can be embedded in the format string. They are shown without the optional field width and precision specification, and are replaced by the indicated characters in the strftime() result:

Directive  Meaning  Notes 
%a Locale's abbreviated weekday name.  
%A Locale's full weekday name.  
%b Locale's abbreviated month name.  
%B Locale's full month name.  
%c Locale's appropriate date and time representation.  
%d Day of the month as a decimal number [01,31].  
%H Hour (24-hour clock) as a decimal number [00,23].  
%I Hour (12-hour clock) as a decimal number [01,12].  
%j Day of the year as a decimal number [001,366].  
%m Month as a decimal number [01,12].  
%M Minute as a decimal number [00,59].  
%p Locale's equivalent of either AM or PM.  
%S Second as a decimal number [00,61]. (1)
%U Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.  
%w Weekday as a decimal number [0(Sunday),6].  
%W Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.  
%x Locale's appropriate date representation.  
%X Locale's appropriate time representation.  
%y Year without century as a decimal number [00,99].  
%Y Year with century as a decimal number.  
%Z Time zone name (or by no characters if no time zone exists).  
%% A literal "%" character.  

Notes:

(1)
The range really is 0 to 61; this accounts for leap seconds and the (very rare) double leap seconds.

Here is an example, a format for dates compatible with that specified in the RFC 2822 Internet email standard. 6.1

>>> from time import gmtime, strftime
>>> strftime("%a, %d %b %Y %H:%M:%S +0000", gmtime())
'Thu, 28 Jun 2001 14:17:15 +0000'

Additional directives may be supported on certain platforms, but only the ones listed here have a meaning standardized by ANSI C.

On some platforms, an optional field width and precision specification can immediately follow the initial "%" of a directive in the following order; this is also not portable. The field width is normally 2 except for %j where it is 3.

strptime(string[, format])
Parse a string representing a time according to a format. The return value is a tuple as returned by gmtime() or localtime(). The format parameter uses the same directives as those used by strftime(); it defaults to "%a %b %d %H:%M:%S %Y" which matches the formatting returned by ctime(). The same platform caveats apply; see the local Unix documentation for restrictions or additional supported directives. If string cannot be parsed according to format, ValueError is raised. Values which are not provided as part of the input string are filled in with default values; the specific values are platform-dependent as the XPG standard does not provide sufficient information to constrain the result.

Note: This function relies entirely on the underlying platform's C library for the date parsing, and some of these libraries are buggy. There's nothing to be done about this short of a new, portable implementation of strptime().

Availability: Most modern Unix systems.

time()
Return the time as a floating point number expressed in seconds since the epoch, in UTC. Note that even though the time is always returned as a floating point number, not all systems provide time with a better precision than 1 second. While this function normally returns non-decreasing values, it can return a lower value than a previous call if the system clock has been set back between the two calls.

timezone
The offset of the local (non-DST) timezone, in seconds west of UTC (negative in most of Western Europe, positive in the US, zero in the UK).

tzname
A tuple of two strings: the first is the name of the local non-DST timezone, the second is the name of the local DST timezone. If no DST timezone is defined, the second string should not be used.

See Also:

Module locale:
Internationalization services. The locale settings can affect the return values for some of the functions in the time module.


Footnotes

... standard.6.1
The use of %Z is now deprecated, but the %z escape that expands to the preferred hour/minute offset is not supported by all ANSI C libraries. Also, a strict reading of the original 1982 RFC 822 standard calls for a two-digit year (%y rather than %Y), but practice moved to 4-digit years long before the year 2000. The 4-digit year has been mandated by RFC 2822, which obsoletes RFC 822.
See About this document... for information on suggesting changes.