6.2 Built-in Module time

This module provides various time-related functions. It is always available.

An explanation of some terminology and conventions is in order.

• The ``epoch'' is the point where the time starts. On January 1st of that year, at 0 hours, the ``time since the epoch'' is zero. For UNIX, the epoch is 1970. To find out what the epoch is, look at gmtime(0).
• UTC is Coordinated Universal Time (formerly known as Greenwich Mean Time). The acronym UTC is not a mistake but a compromise between English and French.
• DST is Daylight Saving Time, an adjustment of the timezone by (usually) one hour during part of the year. DST rules are magic (determined by local law) and can change from year to year. The C library has a table containing the local rules (often it is read from a system file for flexibility) and is the only source of True Wisdom in this respect.
• The precision of the various real-time functions may be less than suggested by the units in which their value or argument is expressed. E.g. on most UNIX systems, the clock ``ticks'' only 50 or 100 times a second, and on the Mac, times are only accurate to whole seconds.
• The time tuple as returned by gmtime() and localtime(), or as accpted by mktime() is a tuple of 9 integers: year (e.g. 1993), month (1-12), day (1-31), hour (0-23), minute (0-59), second (0-59), weekday (0-6, monday is 0), Julian day (1-366) and daylight savings flag (-1, 0 or 1). Note that unlike the C structure, the month value is a range of 1-12, not 0-11. A year value of < 100 will typically be silently converted to 1900 + year value. A -1 argument as daylight savings flag, passed to mktime() will usually result in the correct daylight savings state to be filled in.

The module defines the following functions and data items:

altzone

The offset of the local DST timezone, in seconds west of the 0th meridian, if one is defined. Negative if the local DST timezone is east of the 0th meridian (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'. Note: unlike the C function of the same name, there is no trailing newline.

clock()

Return the current CPU time as a floating point number expressed in seconds. The precision, and in fact the very definiton of the meaning of ``CPU time'', depends on that of the C function of the same name.

ctime(secs)

Convert a time expressed in seconds since the epoch to a string representing local time. ctime(t) is equivalent to asctime(localtime(t)).

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. Fractions of a second are ignored.

localtime(secs)

Like gmtime but converts to local time. The dst flag is set to 1 when DST applies to the given time.

mktime(tuple)

This is the inverse function of localtime. Its argument is the full 9-tuple (since the dst flag is needed -- pass -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.time(). If the input value can't be represented as a valid time, OverflowError is raised.