Islamic/Hijri Calendar
- Lunar, contains 12 months based on motion of moon
- 12 synodic months only 354.36 days, Islamic calendar consistently shorter than tropical year
- based on Qur’an (Sura IX, 36-37)
- Names of the 12 months:
1 |
Muharram |
2 |
Safar |
3 |
Rabi’ al-awwal
(Rabi’ I) |
4 |
Rabi’ al-thani
(Rabi’ II) |
5 |
Jumanda al-awwal (Jumada I) |
6 |
Jumada al-thani
(Jumada II) |
7 |
Rajab |
8 |
Sha’ban |
9 |
Ramadan |
10 |
Shawwal |
11 |
Dhu al-Qi’dah |
12 |
Dhu al-Hijjah |
- A month starts when the lunar crescent is first seen
- some Muslims depend on local sighting of moon, others depend on officials, leads to different starting days of the months
- can’t print a reliable Islamic calendar in advance
- Approximate cycle:
- 30 year cycle with 19 normal years (354 days) and 11 leap years (355 days)
- average length of year 354.365 days
- average synodic month length of 29.53055 days
- calendar slips 1 day with respect to Moon every 2525 years
- counting years
- years counted since Hijra (Mohammed’s emigration to Medina in AD 622)
- 16 July (Julian Calendar) of that year, AH (Anno Hegirae=year of the Hijra) 1 started
- 1st day of 5th month of AD 20874 in Gregorian Calendar will also be (approx.) 1st day of 5th month of AH 20874 of Islamic calendar (when Islamic calendar overtakes Gregorian Calendar)