pgm 13.2 - use local static var so we do the time() sys-call no more than once
pgm 13.2 - validate date, reprompt if bad
pgm 13.2 -- accept and sort on time as well as date
pgm 13.2 - require time; ensure no previous time/date field value is reused if skipped on current entry; the only way to make this program NOT suck would be to get rid of scanf()