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Index: lib/libc/gen/time.3
===================================================================
--- lib/libc/gen/time.3
+++ lib/libc/gen/time.3
@@ -32,7 +32,7 @@
.\" @(#)time.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
-.Dd March 4, 2022
+.Dd April 3, 2022
.Dt TIME 3
.Os
.Sh NAME
@@ -49,7 +49,7 @@
.Fn time
function
returns the value of time in seconds since 0 hours, 0 minutes,
-0 seconds, January 1, 1970, Coordinated Universal Time.
+0 seconds, January 1, 1970, Coordinated Universal Time (UTC).
If an error occurs,
.Fn time
returns the value
@@ -73,12 +73,62 @@
The
.Nm
function conforms to
-.St -p1003.1-2001 .
+.St -p1003.1-2008 .
.Sh HISTORY
A
.Fn time
-function appeared in
-.At v6 .
+system call first appeared in
+.At v1 .
+The
+.At v1
+and
+.At v2
+returned the time after the January 1, 1971.
+The version of
+.At v3
+counted time in sixtieths of a second with a 32-bit return value,
+ensuring an integer overflow crisis every 2.26 years.
+Due to challenges in reconstructing dates from tapes the count was
+changed to a new epoch and the returned time was the count from
+January 1, 1972.
+.Pp
+In
+.At v4
+the granularity of the return value was reduced to whole seconds,
+delaying the aforementioned crisis until 2038.
+.Pp
+.At v7
+introduced the
+.Fn ftime
+system call, which returned time at a millisecond level,
+though retained the
+.Fn gtime
+system call (exposed as
+.Fn time
+in userland).
+.Fn time
+could have been implemented as a wrapper around
+.Fn ftime ,
+but that wasn't done.
+.Pp
+.Bx 4.1c
+implemented a higher-precision time function
+.Fn gettimeofday
+to replace
+.Fn ftime
+and reimplemented
+.Fn time
+in terms of that.
+.Pp
+Since
+.Fx 9
+the implementation of
+.Fn time
+uses
+.Fn clock_gettime "CLOCK_SECOND"
+instead of
+.Fn gettimeofday
+for performance reasons.
.Sh BUGS
Neither
.St -isoC-99

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