1.\" $NetBSD: offtime.3,v 1.4 2017/10/25 19:01:25 abhinav Exp $ 2.\" Written by Klaus Klein, May 10, 2004. 3.\" Public domain. 4.Dd April 14, 2011 5.Dt OFFTIME 3 6.Os 7.Sh NAME 8.Nm offtime , 9.Nm offtime_r , 10.Nm timeoff , 11.Nm timegm , 12.Nm timelocal 13.Nd convert date and time 14.Sh LIBRARY 15.Lb libc 16.Sh SYNOPSIS 17.In time.h 18.Ft struct tm * 19.Fn offtime "const time_t * clock" "long int offset" 20.Ft struct tm * 21.Fn offtime_r "const time_t * clock" "long int offset" "struct tm *ret" 22.Ft time_t 23.Fn timeoff "struct tm * tm" "long int offset" 24.Ft time_t 25.Fn timegm "struct tm * tm" 26.Ft time_t 27.Fn timelocal "struct tm * tm" 28.Sh DESCRIPTION 29These functions are inspired by C standard interfaces named similarly. 30.Pp 31.Fn offtime 32converts the calendar time 33.Fa clock , 34offset by 35.Fa offset 36seconds, 37into broken-down time, expressed as Coordinated Universal Time (UTC). 38.Pp 39.Fn offtime_r 40is similar to 41.Fn offtime 42but it places the returned 43.Ft "struct tm *" 44in the user supplied 45.Fa ret 46argument. 47.Pp 48.Fn timeoff 49converts the broken-down time 50.Fa tm , 51expressed as UTC, 52offset by 53.Fa offset 54seconds, 55into a calendar time value. 56.Pp 57.Fn timegm 58converts the broken-down time 59.Fa tm 60into a calendar time value, effectively being the inverse of 61.Xr gmtime 3 . 62It is equivalent to the C standard function 63.Xr mktime 3 64operating in UTC. 65.Pp 66.Fn timelocal 67converts the broken down time 68.Fa tm , 69expressed as local time, into a calendar time value. 70It is equivalent to the C standard function 71.Xr mktime 3 , 72and is provided for symmetry only. 73.Sh SEE ALSO 74.Xr ctime 3 , 75.Xr tm 3 , 76.Xr tzset 3 77