-Each of these functions returns the value described, or NULL
-(\-1 in case of
-.BR mktime ())
-in case an error was detected.
+On success,
+.BR gmtime ()
+and
+.BR localtime ()
+return a pointer to a
+.IR "struct\ tm" .
+.PP
+On success,
+.BR gmtime_r ()
+and
+.BR localtime_r ()
+return the address of the structure pointed to by
+.IR result .
+.PP
+On success,
+.BR asctime ()
+and
+.BR ctime ()
+return a pointer to a string.
+.PP
+On success,
+.BR asctime_r ()
+and
+.BR ctime_r ()
+return a pointer to the string pointed to by
+.IR buf .
+.PP
+On success,
+.BR mktime ()
+returns the calendar time (seconds since the Epoch),
+expressed as a value of type
+.IR time_t .
+.PP
+On error,
+.BR mktime ()
+returns the value
+.IR "(time_t)\ -1" .
+The remaining functions return NULL on error.
+On error,
+.I errno
+is set to indicate the cause of the error.
+.SH ERRORS
+.TP
+.B EOVERFLOW
+The result cannot be represented.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.ad l
+.TS
+allbox;
+lbw14 lb lbw31
+l l l.
+Interface Attribute Value
+T{
+.BR asctime ()
+T} Thread safety MT-Unsafe race:asctime locale
+T{
+.BR asctime_r ()
+T} Thread safety MT-Safe locale
+T{
+.BR ctime ()
+T} Thread safety T{
+MT-Unsafe race:tmbuf
+.br
+race:asctime env locale
+T}
+T{
+.BR ctime_r (),
+.BR gmtime_r (),
+.BR localtime_r (),
+.BR mktime ()
+T} Thread safety MT-Safe env locale
+T{
+.BR gmtime (),
+.BR localtime ()
+T} Thread safety MT-Unsafe race:tmbuf env locale
+.TE
+.ad