stime.2, time.2, utimensat.2, ctime.3, difftime.3, ftime.3, getspnam.3, mq_receive.3, mq_send.3, rtime.3, sem_wait.3, strftime.3, strptime.3, timeradd.3, rtc.4, core.5, proc.5, icmp.7, time.7: Global fix: Consistently define the Epoch

All definitions of the Epoch have been refactored to the following:

  1970-01-01 00:00:00 +0000 (UTC)

That form is more consistent, logical, precise, and internationally
recognizable than the other variants.

Also, some wording has been altered as well.

Signed-off-by: Michael Witten <mfwitten@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/stime.2

@@ -45,8 +45,8 @@ _SVID_SOURCE
 .SH DESCRIPTION
 .BR stime ()
 sets the system's idea of the time and date.
-Time, pointed
-to by \fIt\fP, is measured in seconds from 00:00:00 UTC January 1, 1970.
+The time, pointed
+to by \fIt\fP, is measured in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 .BR stime ()
 may only be executed by the superuser.
 .SH "RETURN VALUE"

man2/time.2

@@ -35,8 +35,8 @@ time \- get time in seconds
 .BI "time_t time(time_t *" t );
 .SH DESCRIPTION
 .BR time ()
-returns the time since the Epoch
-(00:00:00 UTC, January 1, 1970), measured in seconds.
+returns the time as the number of seconds since the Epoch,
+1970-01-01 00:00:00 +0000 (UTC).
 
 If
 .I t

man2/utimensat.2

@@ -84,9 +84,9 @@ specifies the new "last access time" (\fIatime\fP);
 specifies the new "last modification time" (\fImtime\fP).
 Each of the elements of
 .I times
-specifies a time in seconds and nanoseconds
-since the Epoch (00:00:00, 1 Jan 1970, UTC),
-in a structure of the following form:
+specifies a time as the the number of seconds and nanoseconds
+since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
+This information is conveyed in a structure of the following form:
 .in +4n
 .nf
 

man3/ctime.3

@@ -78,8 +78,7 @@ and
 functions all take
 an argument of data type \fItime_t\fP which represents calendar time.
 When interpreted as an absolute time value, it represents the number of
-seconds elapsed since 00:00:00 on January 1, 1970, Coordinated Universal
-Time (UTC).
+seconds elapsed since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 .PP
 The
 .BR asctime ()

man3/difftime.3

@@ -40,9 +40,9 @@ The
 function returns the number of seconds elapsed
 between time \fItime1\fP and time \fItime0\fP, represented as a
 .IR double .
-The two times are specified in calendar time, which represents the time
-elapsed since the Epoch
-(00:00:00 on January 1, 1970, Coordinated Universal Time (UTC)).
+Each of the times is specified in calendar time, which means its
+value is a measurement (in seconds) relative to the Epoch,
+1970-01-01 00:00:00 +0000 (UTC).
 .SH "CONFORMING TO"
 SVr4, 4.3BSD, C89, C99.
 .SH NOTES

man3/ftime.3

@@ -36,8 +36,8 @@ ftime \- return date and time
 .sp
 .BI "int ftime(struct timeb *" tp );
 .SH DESCRIPTION
-This function returns the current time, in seconds and milliseconds
-since the Epoch (00:00:00 UTC, 1 January 1970).
+This function returns the current time as seconds and milliseconds
+since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 The time is returned in
 .IR tp ,
 which is declared as follows:

man3/getspnam.3

@@ -194,7 +194,7 @@ struct spwd {
     char *sp_namp;     /* Login name */
     char *sp_pwdp;     /* Encrypted password */
     long  sp_lstchg;   /* Date of last change (measured
-                          in days since 1 Jan 1970) */
+                          in days since 1970-01-01 00:00:00 +0000 (UTC)) */
     long  sp_min;      /* Min # of days between changes */
     long  sp_max;      /* Max # of days between changes */
     long  sp_warn;     /* # of days before password expires
@@ -202,7 +202,7 @@ struct spwd {
     long  sp_inact;    /* # of days after password expires
                           until account is disabled */
     long  sp_expire;   /* Date when account expires (measured
-                          in days since 1 Jan 1970) */
+                          in days since 1970-01-01 00:00:00 +0000 (UTC)) */
     unsigned long sp_flag;  /* Reserved */
 };
 .fi

man3/mq_receive.3

@@ -83,7 +83,7 @@ flag is not enabled for the message queue description, then
 points to a structure which specifies a ceiling on the time for which
 the call will block.
 This ceiling is an absolute timeout in seconds and nanoseconds
-since the Epoch (midnight on the morning of 1 January 1970),
+since the Epoch, 1970-01-01 00:00:00 +0000 (UTC), and it is
 specified in the following structure:
 .sp
 .in +4n

man3/mq_send.3

@@ -89,7 +89,7 @@ flag is not enabled for the message queue description, then
 points to a structure which specifies a ceiling on the time for which
 the call will block.
 This ceiling is an absolute timeout in seconds and nanoseconds
-since the Epoch (midnight on the morning of 1 January 1970),
+since the Epoch, 1970-01-01 00:00:00 +0000 (UTC), and it is
 specified in the following structure:
 .sp
 .in +4n

man3/rtime.3

@@ -22,8 +22,8 @@ RFC\ 868 to obtain the time from a remote machine.
 The Time Server Protocol gives the time in seconds since
 00:00:00 UTC, 1 Jan 1900,
 and this function subtracts the appropriate constant in order to
-convert the result to seconds since
-00:00:00 UTC, 1 Jan 1970, the Unix Epoch.
+convert the result to seconds since the Epoch,
+1970-01-01 00:00:00 +0000 (UTC).
 .LP
 When
 .I timeout

man3/sem_wait.3

@@ -77,7 +77,7 @@ should block if the decrement cannot be immediately performed.
 The
 .I abs_timeout
 argument points to a structure that specifies an absolute timeout
-in seconds and nanoseconds since the Epoch (00:00:00, 1 January 1970).
+in seconds and nanoseconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 This structure is defined as follows:
 
 .nf

man3/strftime.3

@@ -182,8 +182,7 @@ For a version including the seconds, see
 below.
 .TP
 .B %s
-The number of seconds since the Epoch, that is, since 1970-01-01
-00:00:00 UTC. (TZ)
+The number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC). (TZ)
 .TP
 .B %S
 The second as a decimal number (range 00 to 60).

man3/strptime.3

@@ -374,8 +374,7 @@ is accepted as a synonym for
 Finally
 .TP
 .B %s
-The number of seconds since the Epoch,
-that is, since 1970-01-01 00:00:00 UTC.
+The number of seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 Leap seconds are not counted unless leap second support is available.
 .LP
 The glibc implementation does not require whitespace between

man3/timeradd.3

@@ -96,8 +96,7 @@ zeros out the
 .I timeval
 structure pointed to by
 .IR tvp ,
-so that it represents the time at midnight
-on the morning of 1 January 1970 (the Epoch).
+so that it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).
 
 .BR timerisset ()
 returns true (nonzero) if either field of the

man4/rtc.4

@@ -59,7 +59,7 @@ and
 .BR time (2),
 as well as setting timestamps on files, etc.
 The system clock reports seconds and microseconds since a start point,
-defined to be the POSIX Epoch: Jan 1, 1970, 0:00 UTC.
+defined to be the POSIX Epoch: 1970-01-01 00:00:00 +0000 (UTC).
 (One common implementation counts timer interrupts, once
 per "jiffy", at a frequency of 100, 250, or 1000 Hz.)
 That is, it is supposed to report wall clock time, which RTCs also do.

man5/core.5

@@ -125,7 +125,7 @@ PID of dumped process
 number of signal causing dump
 .TP
 %t
-time of dump, expressed as seconds since the Epoch (00:00h, 1\ Jan 1970, UTC)
+time of dump, expressed as seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC)
 .TP
 %h
 hostname (same as \fInodename\fP returned by \fBuname\fP(2))

man5/proc.5

@@ -1683,7 +1683,7 @@ each subsequent column is the total for a particular interrupt.
 The number of context switches that the system underwent.
 .TP
 \fIbtime 769041601\fP
-boot time, in seconds since the Epoch (January 1, 1970).
+boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 .TP
 \fIprocesses 86031\fP
 Number of forks since boot.

man7/icmp.7

@@ -176,7 +176,7 @@ routing table and the redirect routes are expired after some time.
 .PP
 The 64-bit timestamp returned by
 .B ICMP_TIMESTAMP
-is in milliseconds since January 1, 1970.
+is in milliseconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
 .PP
 Linux ICMP internally uses a raw socket to send ICMPs.
 This raw socket may appear in

man7/time.7

@@ -124,7 +124,7 @@ HRTs are not supported on all hardware architectures.
 .SS "The Epoch"
 Unix systems represent time in seconds since the
 .IR Epoch ,
-which is defined as 0:00:00 UTC on the morning of 1 January 1970.
+1970-01-01 00:00:00 +0000 (UTC).
 
 A program can determine the
 .I "calendar time"