Determines if the ClockData structure contains legal date information and returns the number of seconds from 01-Jan-1978 to that date, or 0 if the ClockData structure contains illegal data.
INPUTS
date
a filled-in ClockData structure
RESULT
seconds
0 if date is invalid, otherwise the number of seconds from 01-Jan-1978 to the date
BUGS
The wday field of the ClockData structure is not checked.