The second verse (37) also refers to this very custom of Jahiliyyah by saying: اِنَّمَا الںَّسِٓیُ زِیَادَۃُ فِی الکُفرِ (... is nothing but an increase in the infidelity). The word: نَسِیی (nasi’) is a verbal noun that means to move back or postpone. It is also used in the sense of that which is delayed (mu'akhkhar).
By putting these months back and forth, the Mushriks of Arabia thought, they would be achieving two things - that it will serve their material interests and that it would also give them the credit of complying with the Divine injunction. This approach was not approved by Allah Ta` ala for their act of postponing and moving months from where they belonged was nothing but an addition to their stance of denial which was going to lead them further astray. That they go about declaring that a sacred month was not sacred in some year and then be ready to name it as sacred in some other year was simply unacceptable. The sentence: لِّيُوَاطِئُوا عِدَّةَ مَا حَرَّمَ اللَّـهُ (so that they may conform [ only ] to the number of what Allah has sanctified) following soon after means that a mere act of conforming to the given number cannot stand for the correct compliance of the injunction. The truth of the matter is that the month for which the injunction has been given should be the month in which the injunction must be carried out. This is imperative.
Injunctions and Rulings
The verses cited above prove that the order of months and the names by which they are known in Islam should not be taken as terms coined by human beings. In fact, the day the Lord of all the worlds created the heavens and the Earth, He had also settled this order and these names and, along with it, particular injunctions to be carried out during particular months. From here, we also come to know that, in all Islamic legal injunctions, only lunar months are credible in the sight of Allah Ta'ala. In other words, all injunctions of the Shari’ ah of Islam - such as, fasting, Hajj, Zakah and many others - relate to the lunar calendar. But, when it comes to finding out the day, date and year, the way the Holy Qur'an has declared the Moon as its indicator, it has, very similarly, identified the Sun too as the other sign: لِتعلَمُوا عَدَہَ السِّنِینَ وَالحِسَاب (so that you may know the number of years and the count [ of time ] - 10:5). Therefore, keeping track of days and years through a lunar or solar calendar is equally permissible. But, Allah Ta` ala has favored the lunar calendar for His injunctions and has made it the pivot round which the laws of the Shari’ ah of Islam revolve. Therefore, the preservation of the lunar calendar is Fard al-Kifayah (a religious obligation which, if fulfilled by some, will absolve others). If the entire community of Muslims were to abandon the lunar calendar and forget all about it, then, everyone will be a sinner. However, if it remains viably preserved, the use of another calendar is also permissible - but, there is no doubt that it is against the way of Allah and the way of the worthy forbears of Islam - therefore, it is not good to opt for it unnecessarily.
The month intercalated to complete the count of years has also been considered by some as impermissible under this verse. But, that is not correct because the system of reckoning under which the intercalation of a month is made has nothing to do with the laws of the Shari’ ah of Islam. The people of Jihiliyyah changed these religious laws by adding to the lunar and legal months, therefore, they were censured. As for the practice of intercalation, it does not affect Islamic legal injunctions, therefore, it is not included under this prohibition.