curl/docs/libcurl/curl_getdate.3

.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" * SPDX-License-Identifier: curl
.\" *
.\" **************************************************************************
.TH curl_getdate 3 "12 Aug 2005" "libcurl 7.0" "libcurl Manual"
.SH NAME
curl_getdate - Convert a date string to number of seconds
.SH SYNOPSIS
.nf
#include <curl/curl.h>

time_t curl_getdate(char *datestring, time_t *now);
.fi
.SH DESCRIPTION
\fIcurl_getdate(3)\fP returns the number of seconds since the Epoch, January
1st 1970 00:00:00 in the UTC time zone, for the date and time that the
\fIdatestring\fP parameter specifies. The \fInow\fP parameter is not used,
pass a NULL there.

This function works with valid dates and does not always detect and reject
wrong dates, such as February 30.

.SH PARSING DATES AND TIMES
A "date" is a string containing several items separated by whitespace. The
order of the items is immaterial. A date string may contain many flavors of
items:
.TP 0.8i
.B calendar date items
Can be specified several ways. Month names can only be three-letter English
abbreviations, numbers can be zero-prefixed and the year may use 2 or 4
digits.  Examples: 06 Nov 1994, 06-Nov-94 and Nov-94 6.
.TP
.B time of the day items
This string specifies the time on a given day. You must specify it with 6
digits with two colons: HH:MM:SS. To not include the time in a date string,
will make the function assume 00:00:00. Example: 18:19:21.
.TP
.B time zone items
Specifies international time zone. There are a few acronyms supported, but in
general you should instead use the specific relative time compared to
UTC. Supported formats include: -1200, MST, +0100.
.TP
.B day of the week items
Specifies a day of the week. Days of the week may be spelled out in full
(using English): `Sunday', `Monday', etc or they may be abbreviated to their
first three letters. This is usually not info that adds anything.
.TP
.B pure numbers
If a decimal number of the form YYYYMMDD appears, then YYYY is read as the
year, MM as the month number and DD as the day of the month, for the specified
calendar date.
.SH EXAMPLE
.nf
 time_t t;
 t = curl_getdate("Sun, 06 Nov 1994 08:49:37 GMT", NULL);
 t = curl_getdate("Sunday, 06-Nov-94 08:49:37 GMT", NULL);
 t = curl_getdate("Sun Nov  6 08:49:37 1994", NULL);
 t = curl_getdate("06 Nov 1994 08:49:37 GMT", NULL);
 t = curl_getdate("06-Nov-94 08:49:37 GMT", NULL);
 t = curl_getdate("Nov  6 08:49:37 1994", NULL);
 t = curl_getdate("06 Nov 1994 08:49:37", NULL);
 t = curl_getdate("06-Nov-94 08:49:37", NULL);
 t = curl_getdate("1994 Nov 6 08:49:37", NULL);
 t = curl_getdate("GMT 08:49:37 06-Nov-94 Sunday", NULL);
 t = curl_getdate("94 6 Nov 08:49:37", NULL);
 t = curl_getdate("1994 Nov 6", NULL);
 t = curl_getdate("06-Nov-94", NULL);
 t = curl_getdate("Sun Nov 6 94", NULL);
 t = curl_getdate("1994.Nov.6", NULL);
 t = curl_getdate("Sun/Nov/6/94/GMT", NULL);
 t = curl_getdate("Sun, 06 Nov 1994 08:49:37 CET", NULL);
 t = curl_getdate("06 Nov 1994 08:49:37 EST", NULL);
 t = curl_getdate("Sun, 12 Sep 2004 15:05:58 -0700", NULL);
 t = curl_getdate("Sat, 11 Sep 2004 21:32:11 +0200", NULL);
 t = curl_getdate("20040912 15:05:58 -0700", NULL);
 t = curl_getdate("20040911 +0200", NULL);
.fi
.SH STANDARDS
This parser handles date formats specified in RFC 822 (including the update in
RFC 1123) using time zone name or time zone delta and RFC 850 (obsoleted by
RFC 1036) and ANSI C's \fIasctime()\fP format. These formats are the only ones
RFC 7231 says HTTP applications may use.
.SH AVAILABILITY
Always
.SH RETURN VALUE
This function returns -1 when it fails to parse the date string. Otherwise it
returns the number of seconds as described.

On systems with a signed 32 bit time_t: if the year is larger than 2037 or
less than 1903, this function will return -1.

On systems with an unsigned 32 bit time_t: if the year is larger than 2106 or
less than 1970, this function will return -1.

On systems with 64 bit time_t: if the year is less than 1583, this function
will return -1. (The Gregorian calendar was first introduced 1582 so no "real"
dates in this way of doing dates existed before then.)
.SH "SEE ALSO"
.BR curl_easy_escape "(3), " curl_easy_unescape "(3), "
.BR CURLOPT_TIMECONDITION "(3), " CURLOPT_TIMEVALUE "(3) "