.B -n
Report the date as the number of seconds since the
epoch, 00:00:00 GMT, January 1, 1970.
+.TP
+.B -i
+Report the date as ISO-8601 without time and timezone suffix.
+.TP
+.B -t
+Report the date as ISO-8601 with time and timezone suffix.
.PP
The conversion from Greenwich Mean Time to local time depends on the
.B $timezone