GNU Info

(libc.info)Calendar Time

---

Next: Setting an Alarm Prev: Processor And CPU Time Up: Date and Time

---

Enter node , (file) or (file)node

Calendar Time
=============

   This section describes facilities for keeping track of calendar time.
Note: Time Basics.

   The GNU C library represents calendar time three ways:

   * "Simple time" (the `time_t' data type) is a compact
     representation, typically giving the number of seconds of elapsed
     time since some implementation-specific base time.

   * There is also a "high-resolution time" representation.  Like simple
     time, this represents a calendar time as an elapsed time since a
     base time, but instead of measuring in whole seconds, it uses a
     `struct timeval' data type, which includes fractions of a second.
     Use this time representation instead of simple time when you need
     greater precision.

   * "Local time" or "broken-down time" (the `struct tm' data type)
     represents a calendar time as a set of components specifying the
     year, month, and so on in the Gregorian calendar, for a specific
     time zone.  This calendar time representation is usually used only
     to communicate with people.

Simple Calendar Time

Facilities for manipulating calendar time.

High-Resolution Calendar

A time representation with greater precision.

Broken-down Time

Facilities for manipulating local time.

High Accuracy Clock

Maintaining a high accuracy system clock.

Formatting Calendar Time

Converting times to strings.

Parsing Date and Time

Convert textual time and date information back

into broken-down time values.

TZ Variable

How users specify the time zone.

Time Zone Functions

Functions to examine or specify the time zone.

Time Functions Example

An example program showing use of some of

the time functions.