The following two functions are available for getting the current time of day, and for formatting time stamps. They are specific to gawk.

systime(): returns the current time of day as the number of seconds since a particular epoch (Midnight, January 1, 1970 UTC, on POSIX systems).
strftime([format[, timestamp]]): formats timestamp according to the specification in format. The current time of day is used if no timestamp is supplied. A default format equivalent to the output of the date utility is used if no format is supplied. See section Functions for Dealing with Time Stamps, for the details on the conversion specifiers that strftime accepts.

See section Built-in Functions, for a description of all of awk's built-in functions.