The Islamic Calendar, used by
Muslims, is based on the
moon. It has 12
months of either 29 or 30 days. Eleven times, every 30 years, an extra day is added to keep the calendar in time with the
moon, not the
seasons.
Since the Islamic year is just 354 or 355 days long, holidays move backward through the seasons, and each year, a holiday comes eleven days or sooner. In 33 years, the holiday is back where it started.
Year 1 on the Islamic Calendar was 622 on the Gregorian Calendar, while 1420 was 2000.
Islamic Calendar
Month Days
1. Muharram 30
2. Safar 29
3. Rabi I 30
4. Rabi II 29
5. Jumada I 30
6. Jumada II 29
7. Rajab 30
8. Shaban 29
9. Ramadan 30
10. Shawwal 29
11. Zulkadah 30
12. Zulhijjah 29