Calendar facts:

average-month ( -- value )

months-per-year ( -- value )

days-per-year ( -- value )

hours-per-year ( -- value )

minutes-per-year ( -- value )

seconds-per-year ( -- value )

days-in-month ( timestamp -- n )

day-of-year ( timestamp -- n )

day-of-week ( timestamp -- n )

week-number ( timestamp -- [1,53] )

Calculating a Julian day number:

julian-day-number ( $year $month $day -- n )

Calculate a timestamp:

julian-day-number>date ( $n -- year month day )