Where the day or month is '08' or '09' then some browsers will assume the leading zero makes the number octal rather than decimal and since in base 8 you count 01, 02, 03, 04, 05, 06, 07, 010, 011 and there are no such numbers as 8 and 9 the person who wrote the code is left wondering why they are getting 0 when they expected 8 or 9.