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sf_time(3) FreeBSD Library Functions Manual sf_time(3)

strtotime, timetostr
date and time conversions.

#include <strfunc.h>
strtotime(char *datestring);
char *
timetostr(time_t value, int flags);

Those functions used to convert time format from string to binary time_t and vice versa.
strtotime(char *) takes one string argument that represents the date and time in a number of formats, briefly shown below. strtotime() is immune to trailing spaces, newlines and other non-printable and printable tails. It also tries to recognize elder time formats variants and strings created by broken implementations.
1. ISO-8601 notation. This form best suited for use in mixed human/automatic parsing and comparisons. The typical date string looks like:
2. RFC-822 (updated by RFC-1123). This form used in the E-mail headers, like "Data:" and other. The date in this format looks like:
Sat, 30 Sep 2000 17:24:58 +0400 (MSD) 
Sat, 30 Sep 2000 17:24:58 +0400 
or even 
Sat, 30 Sep 2000 17:24:58 MSD 
that is but widely used, but lame, 
though correctly handled by strtotime.
3. ctime(3) or asctime(3) form:
Sat Sep 30 17:24:58 2000
4. Syslog daemon's form:
Mar 23 19:07:43
5. Unix time in numeric form. This form specifies the number of seconds passed since the Epoch (00:00:00 UTC, January 1, 1970; see time(3) ). Typical form is "970257600" (signed long number).
Other types. A set of other formats that are widely used is supported too.
Thursday, 10-Jun-93 01:29:59 GMT 
Thu, 10 Jan 1993 01:29:59 GMT 
Wed Jun  9 01:29:59 1993 GMT 
1997/06/23 13:22:33 
and derivatives.
Support for other time representation formats can be added upon request.
timetostr(time_t value, int flags) used to convert the time value to the user-specified representation format, specified by flags. Flags are defined in strfunc.h:
TFMT_UNIX - simple numeric unix_time format.
TFMT_CTIME - ctime(3) and asctime(3) format.
TFMT_RFC822 - format defined in RFC's 822 and 1123.
TFMT_X208 - format specified in X.208.
TFMT_ISO8601 - general representation according to ISO-8601 conventions.
Those flags are present to specify the output format. And the following ones exist to slightly modify the output:
TFMT_LOCAL - construct string representing the time within the local timezone instead of default GMT (zero timezone offset).
TFMT_UF - user-friendly output. This flag turns on some additional features like dashes and colons within the ISO-8601 output or timezone abbreviation within the RFC-822 date string.
TFMT_OLD822GMT - use old RFC-822 scheme with the hard-coded GMT zone abbreviation. This flag also disables the TFMT_LOCAL and TFMT_UF flag will be ignored. The typical string in this format will look like "Sat, 30 Sep 2000 21:24:58 GMT". This time format is widely used by the HTTP browsers and CGI scripts to exchange the "expiration" and "modified" times. This flag should be used in conjunction with TFMT_RFC822.
Those flags can be mixed by OR'ing.

The strtotime() function returns the value of given time representation in seconds since 0 hours, 0 minutes, 0 seconds, January 1, 1970, Coordinated Universal Time. If parse error occured, zero is returned and global variable errno is set to EINVAL to indicate an error.
timetostr() always returns pointer to the internal static object with string representation of given time_t value.

void test() { 
	char *timeString = "Sat, 1 Oct 2000 01:34:00 +0400"; 
	time_t timeValue = 970348600; 
	printf("timeString -> time_t: %ld\n", (long)strtotime(timeString)); 
	printf("timeValue -> string: %s\n", 

strfunc(3), ctime(3), asctime(3).

Lev Walkin <>
October 1, 2000 FreeBSD 12.0-RELEASE

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