| <html lang="en"> |
| <head> |
| <title>Calendar Time - The GNU C Library</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="The GNU C Library"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Date-and-Time.html#Date-and-Time" title="Date and Time"> |
| <link rel="prev" href="Processor-And-CPU-Time.html#Processor-And-CPU-Time" title="Processor And CPU Time"> |
| <link rel="next" href="Setting-an-Alarm.html#Setting-an-Alarm" title="Setting an Alarm"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU C library. |
| |
| This is Edition 0.12, last updated 2007-10-27, |
| of `The GNU C Library Reference Manual', for version |
| 2.8 (Sourcery G++ Lite 2011.03-41). |
| |
| Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, |
| 2003, 2007, 2008, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software Needs Free Documentation'' |
| and ``GNU Lesser General Public License'', the Front-Cover texts being |
| ``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A |
| copy of the license is included in the section entitled "GNU Free |
| Documentation License". |
| |
| (a) The FSF's Back-Cover Text is: ``You have the freedom to |
| copy and modify this GNU manual. Buying copies from the FSF |
| supports it in developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Calendar-Time"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Setting-an-Alarm.html#Setting-an-Alarm">Setting an Alarm</a>, |
| Previous: <a rel="previous" accesskey="p" href="Processor-And-CPU-Time.html#Processor-And-CPU-Time">Processor And CPU Time</a>, |
| Up: <a rel="up" accesskey="u" href="Date-and-Time.html#Date-and-Time">Date and Time</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">21.4 Calendar Time</h3> |
| |
| <p>This section describes facilities for keeping track of calendar time. |
| See <a href="Time-Basics.html#Time-Basics">Time Basics</a>. |
| |
| <p>The GNU C library represents calendar time three ways: |
| |
| <ul> |
| <li><dfn>Simple time</dfn> (the <code>time_t</code> data type) is a compact |
| representation, typically giving the number of seconds of elapsed time |
| since some implementation-specific base time. |
| <a name="index-simple-time-2617"></a> |
| <li>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 <code>struct |
| timeval</code> data type, which includes fractions of a second. Use this time |
| representation instead of simple time when you need greater precision. |
| <a name="index-high_002dresolution-time-2618"></a> |
| <li><dfn>Local time</dfn> or <dfn>broken-down time</dfn> (the <code>struct tm</code> 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. |
| <a name="index-local-time-2619"></a><a name="index-broken_002ddown-time-2620"></a><a name="index-Gregorian-calendar-2621"></a><a name="index-calendar_002c-Gregorian-2622"></a></ul> |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Simple-Calendar-Time.html#Simple-Calendar-Time">Simple Calendar Time</a>: Facilities for manipulating calendar time. |
| <li><a accesskey="2" href="High_002dResolution-Calendar.html#High_002dResolution-Calendar">High-Resolution Calendar</a>: A time representation with greater precision. |
| <li><a accesskey="3" href="Broken_002ddown-Time.html#Broken_002ddown-Time">Broken-down Time</a>: Facilities for manipulating local time. |
| <li><a accesskey="4" href="High-Accuracy-Clock.html#High-Accuracy-Clock">High Accuracy Clock</a>: Maintaining a high accuracy system clock. |
| <li><a accesskey="5" href="Formatting-Calendar-Time.html#Formatting-Calendar-Time">Formatting Calendar Time</a>: Converting times to strings. |
| <li><a accesskey="6" href="Parsing-Date-and-Time.html#Parsing-Date-and-Time">Parsing Date and Time</a>: Convert textual time and date information back |
| into broken-down time values. |
| <li><a accesskey="7" href="TZ-Variable.html#TZ-Variable">TZ Variable</a>: How users specify the time zone. |
| <li><a accesskey="8" href="Time-Zone-Functions.html#Time-Zone-Functions">Time Zone Functions</a>: Functions to examine or specify the time zone. |
| <li><a accesskey="9" href="Time-Functions-Example.html#Time-Functions-Example">Time Functions Example</a>: An example program showing use of some of |
| the time functions. |
| </ul> |
| |
| </body></html> |
| |
