— Function: time-less-p t1 t2

This returns t if time value t1 is less than time value t2.

— Function: time-subtract t1 t2

This returns the time difference t1 − t2 between two time values, in the same format as a time value.

— Function: time-add t1 t2

This returns the sum of two time values, one of which ought to represent a time difference rather than a point in time. Here is how to add a number of seconds to a time value:

          (time-add time (seconds-to-time seconds))

— Function: time-to-days time

This function returns the number of days between the beginning of year 1 and time.

— Function: time-to-day-in-year time

This returns the day number within the year corresponding to time.

— Function: date-leap-year-p year

This function returns t if year is a leap year.