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offtime(3) [netbsd man page]

OFFTIME(3)						   BSD Library Functions Manual 						OFFTIME(3)

offtime, timeoff, timegm, timelocal -- convert date and time LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <time.h> struct tm * offtime(const time_t * clock, long int offset); struct tm * offtime_r(const time_t * clock, long int offset, struct tm *ret); time_t timeoff(struct tm * tm, long int offset); time_t timegm(struct tm * tm); time_t timelocal(struct tm * tm); DESCRIPTION
These functions are inspired by C standard interfaces named similarly. offtime() converts the calendar time clock, offset by offset seconds, into broken-down time, expressed as Coordinated Universal Time (UTC). offtime_r() is similar to offtime() but it places the returned struct tm * in the user supplied ret argument. timeoff() converts the broken-down time tm, expressed as UTC, offset by offset seconds, into a calendar time value. timegm() converts the broken-down time tm into a calendar time value, effectively being the inverse of gmtime(3). It is equivalent to the C standard function mktime(3) operating in UTC. timelocal() converts the broken down time tm, expressed as local time, into a calendar time value. It is equivalent to the C standard func- tion mktime(3), and is provided for symmetry only. SEE ALSO
ctime(3), tm(3), tzset(3) BSD
April 14, 2011 BSD

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TIMEGM(3)                                                    Linux Programmer's Manual                                                   TIMEGM(3)

timegm, timelocal - inverses of gmtime and localtime SYNOPSIS
#include <time.h> time_t timelocal(struct tm *tm); time_t timegm(struct tm *tm); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timelocal(), timegm(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE || _SVID_SOURCE DESCRIPTION
The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3). Both functions take a broken-down time and convert it to calendar time (seconds since the Epoch, 1970-01-01 00:00:00 +0000, UTC). The difference between the two functions is that timelo- cal() takes the local timezone into account when doing the conversion, while timegm() takes the input value to be Coordinated Universal Time (UTC). RETURN VALUE
On success, these functions return the calendar time (seconds since the Epoch), expressed as a value of type time_t. On error, they return the value (time_t) -1 and set errno to indicate the cause of the error. ERRORS
EOVERFLOW The result cannot be represented. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +----------------------+---------------+--------------------+ |Interface | Attribute | Value | +----------------------+---------------+--------------------+ |timelocal(), timegm() | Thread safety | MT-Safe env locale | +----------------------+---------------+--------------------+ CONFORMING TO
These functions are nonstandard GNU extensions that are also present on the BSDs. Avoid their use. NOTES
The timelocal() function is equivalent to the POSIX standard function mktime(3). There is no reason to ever use it. SEE ALSO
gmtime(3), localtime(3), mktime(3), tzset(3) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at GNU 2016-12-12 TIMEGM(3)
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