%p is replaced by AM or PM, as appropriate.
%r is a synonym for "%I:%M:%S %p".
%R is a synonym for "%H:%M".
+%s is replaced by the time in seconds since 00:00:00, Jan 1, 1970 (a
+ nonstandard extension)
%S is replaced by the second (00-60).
%t is a synonym for "\\t".
%T is a synonym for "%H:%M:%S".