time.2: Describe EOVERFLOW details

Heavily based on text proposed by Paul Eggert.

Cowritten-by: Paul Eggert <eggert@cs.ucla.edu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/time.2

@@ -82,6 +82,27 @@ and the Epoch, because of leap seconds and because system clocks are not
 required to be synchronized to a standard reference.
 The intention is that the interpretation of seconds since the Epoch values be
 consistent; see POSIX.1-2008 Rationale A.4.15 for further rationale.
+
+On Linux, a call to
+.BR time ()
+with
+.I t
+specified as NULL cannot fail with the error
+.BR EOVERFLOW ,
+even on ABIs where 
+.I time_t
+is a signed 32-bit integer and the clock ticks past the time 2**31 
+(2038-01-19 03:14:08 UTC, ignoring leap seconds).
+(POSIX.1 permits, but does not require, the
+.B EOVERFLOW
+error in the case where the seconds since the Epoch will not fit in
+.IR time_t .)
+Instead, the behavior on Linux is undefined when the system time is out of the
+.I time_t
+range.
+Applications intended to run after 2038 should use ABIs with
+.I time_t
+wider than 32 bits.
 .SH BUGS
 Error returns from this system call are indistinguishable from
 successful reports that the time is a few seconds