assalaamu `alaykum, raHmat Allah wa-barakaatuhu

In the Hebrew calendrical reckoning, there is a concept know as `ibbur (lit., "impregnation") whereby a month is added every so often in order to keep the Spring festivals in the Spring and the Winter festivals in the Winter, etc.

Why does the Hijri calendar continue indefinitely with Ramadan falling in all secular months eventually as it moves across the solar calendar year out of sync? Is there a reason for this? If so, what is it?


  • Just one small point: We ask for God’s blessings (barakātuhu), not for his pond (birkatuhu).
    – aasheq
    Commented Feb 25, 2015 at 11:43
  • @aasheq - Thanks for the correction. My Arabic teacher is Shaami and transliterated it originally as "wa-birkato". That's where I got it from. Salaam.
    – user11749
    Commented Feb 26, 2015 at 13:12
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    A better question is why the Hebrew calendar does have the solar correction. The reason is because the Jewish holidays are tied to particular seasons. If this were not the case, there would be no reason for leap years. A plain lunar calendar is far simpler and easier to deal with than a lunar/solar hybrid calendar.
    – Daniel
    Commented Jul 16, 2015 at 15:21

3 Answers 3


The Muslim tradition says that the ancient Arabs did practice intercalation (nasīʼ), but this was abolished by the Prophet at the time of the “Farewell Pilgrimage” in the year 10 of the Hijra. This is eluded to in Qur’an 9:37:

“nasīʼ is merely an increase in disbelief; those who disbelieved have been misled in (or: by) it, in that they permit it one year and forbid it another year so as to equalise the number of what God forbade and to permit what God forbade”.

إِنَّمَا ٱلنَّسِىٓءُ زِيَادَةٌ۬ فِى ٱلۡڪُفۡرِ‌ۖ يُضَلُّ بِهِ ٱلَّذِينَ كَفَرُواْ يُحِلُّونَهُ ۥ عَامً۬ا وَيُحَرِّمُونَهُ ۥ عَامً۬ا لِّيُوَاطِـُٔواْ عِدَّةَ مَا حَرَّمَ ٱللَّهُ فَيُحِلُّواْ مَا حَرَّمَ ٱللَّهُ

This is a complicated matter and there is a lot of scholarly literature about it.


Quran specifically warns against those adding extra days/months to lunar calendar, which is commonly done to mirror solar year.


As Salaamu alaikum Brother, The Islamic months are calculated based on the cycle of the moon. That is how Prophet Mohammed (PBUH) has taught us to calculate the months. The cycle of moon is 29 or 30 days for every month. We have no right to calculate differently other than what our Prophet Mohammed (PBUH) has taught us. The cycle of the moon also does not sync according to solar calendar. We also cannot change the moons cycle to fit to solar calendar. Allah (SWT) has created it in such a way. We need to accept what the reality is.

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    The cycle of the moon is not interrupted if you intercalate a whole month from time to time.
    – aasheq
    Commented Feb 25, 2015 at 8:27
  • if you intercalate you will not be following the way of calculating the Hijri months based on moon cycle.
    – Dragonborn
    Commented Feb 25, 2015 at 8:37
  • That is not actually true. Think about it. If every month, including the nasi' month, begins with the sighting of the new moon, then there is no interruption of the lunar cycle.
    – aasheq
    Commented Feb 25, 2015 at 8:40
  • Why do you want to intercalate in first place. Al Quran prohibits as from doing that Sura 9 ("At-Tawba"), ayat 36–37. Beside in Nasi' every second or third year the beginning of the year was postponed by one month and breaking the follow up cycle for this postponed month.
    – Dragonborn
    Commented Feb 25, 2015 at 8:49
  • 1
    Al Quran specifically prohibits in At-Tawba 37. if you intercalate in one year, the normal days of the following year will also be displaced and you will obviously displace the sacred months. Besides ALLAH(SWT) simply says At-Tawba 36-37 there are 12 months and intercalation of these 12 months is prohibited - Plain as simple. There is no need to think of any hidden logics.
    – Dragonborn
    Commented Feb 25, 2015 at 9:28

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