[izekqsbo] November 30, 1999

If January 1, 2000 is 1-1-00, then one month and one day before that, November 30, 1999, is 0-0-00.

Similarly, if January 1 (any year) is day 1, the December 31 is day 0 (0 day). This might be useful for calculating the day of the year for some other date.