Day of month. Must be from 1 to 31 and valid for the year and month, or 0
if specifying a year by itself or a year and month where the day is not
significant.
Optional month
month:undefined | number
Month of year. Must be from 1 to 12, or 0 if specifying a year without a
month and day.
Optional year
year:undefined | number
Year of date. Must be from 1 to 9999, or 0 if specifying a date without
a year.
Day of month. Must be from 1 to 31 and valid for the year and month, or 0 if specifying a year by itself or a year and month where the day is not significant.