.\"     $NetBSD: clock.9,v 1.2 2014/12/26 14:15:18 wiz Exp $
.\"
.\" Copyright (c) 2014 The NetBSD Foundation, Inc.
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.\" This code is contributed to The NetBSD Foundation by Kamil Rytarowski
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.Dd December 26, 2014
.Dt CLOCK 9
.Os
.Sh NAME
.Nm days_in_month ,
.Nm is_leap_year ,
.Nm days_per_year
.Nd handy time utilities
.Sh SYNOPSIS
.In sys/clock.h
.Vt #define SECS_PER_MINUTE         60
.Vt #define SECS_PER_HOUR           3600
.Vt #define SECS_PER_DAY            86400
.Vt #define DAYS_PER_COMMON_YEAR    365
.Vt #define DAYS_PER_LEAP_YEAR      366
.Vt #define SECS_PER_COMMON_YEAR    (SECS_PER_DAY * DAYS_PER_COMMON_YEAR)
.Vt #define SECS_PER_LEAP_YEAR      (SECS_PER_DAY * DAYS_PER_LEAP_YEAR)
.Ft static inline int
.Fn days_in_month "int m"
.Ft static inline int
.Fn is_leap_year "uint64_t year"
.Ft static inline int
.Fn days_per_year "uint64_t year"
.Sh DESCRIPTION
The
.In sys/clock.h
file provides handy time constants and
.Ft static inline
functions.
.Sh FUNCTIONS
The
.Fn days_in_month
function returns the number of days in the given month.
.Fn days_in_month
assumes 28 days for February.
If the input value is out of the valid range (1-12) then the function returns
\-1.
.Pp
The
.Fn is_leap_year
and
.Fn days_per_year
functions take as the input parameter a value in the Gregorian year format.
.Sh SEE ALSO
.Xr bintime 9 ,
.Xr boottime 9 ,
.Xr time_second 9 ,
.Xr time_uptime 9 ,
.Xr todr_gettime 9
.Sh HISTORY
The
.In sys/clock.h
header with handy utilities originated from
.In dev/clock_subr.h ,
which originated from
.In arch/hp300/hp300/clock.c .
.Pp
The
.In arch/hp300/hp300/clock.c
file first appeared in
.Nx 0.8
as a set of hp300 time-converting functions.
.In dev/clock_subr.h
first appeared in
.Nx 1.3
as a shared list of functions to convert between
.Dq year/month/day/hour/minute/second
and seconds since 1970
.Pq Dq POSIX time .
The
.In sys/clock.h
file first appeared in
.Nx 8 .
.Sh AUTHORS
.An Kamil Rytarowski