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 The
Islamic Calendar
The Islamic calendar (or Hijri calendar) is a purely lunar calendar. It
contains 12 months that are based on the motion of the moon, and because
12 synodic months is only 12 x 29.53=354.36 days, the Islamic calendar
is consistently shorter than a tropical year, and therefore it shifts with
respect to the Christian calendar.
The calendar is based on the Qur'an (Sura IX, 36-37) and its proper
observance is a sacred duty for Muslims.
The Islamic calendar is the official calendar in countries around the
Gulf, especially Saudi Arabia. But other Muslim countries use the Gregorian
calendar for civil purposes and only turn to the Islamic calendar for religious
purposes.
What does an Islamic year
look like?
The names of the 12 months that comprise the Islamic year are:
|
| 1. |
Muharram |
7. |
Rajab |
| 2. |
Safar |
8. |
Sha'ban |
| 3. |
Rabi' al-awwal (Rabi' I) |
9. |
Ramadan |
| 4. |
Rabi' al-thani (Rabi' II) |
10. |
Shawwal |
| 5. |
Jumada al-awwal (Jumada I) |
11. |
Dhu al-Qi'dah |
| 6. |
Jumada al-thani (Jumada II) |
12. |
Dhu al-Hijjah |
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(Due to different transliterations of the Arabic alphabet, other spellings
of the months are possible.)
Each month starts when the lunar crescent is first seen (by a human
observer's eye) after a new moon.
Although new moons may be calculated quite precisely, the actual visibility
of the crescent is much more difficult to predict. It depends on factors
such as weather, the optical properties of the atmosphere, and the location
of the observer. It is therefore very difficult to give accurate information
in advance about when a new month will start.
Furthermore, some Muslims depend on a local sighting of the moon, whereas
others depend on a sighting by authorities somewhere in the Muslim world.
Both are valid Islamic practices, but they may lead to different starting
days for the months.
So you can't print an Islamic
calendar in advance?
Not a reliable one. However, calendars are printed for planning purposes,
but such calendars are based on estimates of the visibility of the lunar
crescent, and the actual month may start a day earlier or later than predicted
in the printed calendar.
Different methods for estimating the calendars are used.
Some sources mention a crude system in which all odd numbered months
have 30 days and all even numbered months have 29 days with an extra day
added to the last month in 'leap years' (a concept otherwise unknown in
the calendar). Leap years could then be years in which the number year
mod 30 is one of the following: 2, 5, 7, 10, 13, 16, 18, 21, 24, 26,
or 29. (This is the algorithm used in the calendar program of the Gnu Emacs
editor.)
Such a calendar would give an average month length of 29.53056 days,
which is quite close to the synodic month of 29.53059 days, so on the
average it would be quite accurate, but in any given month it is still
just a rough estimate.
Better algorithms for estimating the visibility of the new moon have
been devised.
How does one count years?
Years are counted since the Hijra, that is, Mohammed's flight to Medina,
which is assumed to have taken place 16 July C.E. 622 (Julian calendar).
On that date AH 1 started (AH = Anno Hegirae = year of the Hijra).
In the year C.E. 1998 we have witnessed the start of Islamic year AH
1419.
Note that although only 1998 - 622 = 1376 years have passed in the Christian
calendar, 1418 years have passed in the Islamic calendar, because its year
is consistently shorter (by about 11 days) than the tropical year used
by the Christian calendar.
When will the Islamic calendar
overtake the Gregorian calendar?
As the year in the Islamic calendar is about 11 days shorter than the
year in the Christian calendar, the Islamic years are slowly gaining in
on the Christian years. But it will be many years before the two coincide.
The 1st day of the 5th month of C.E. 20874 in the Gregorian calendar will
also be (approximately) the 1st day of the 5th month of AH 20874 of the
Islamic calendar.
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