What is the ruling of Sharia on the declaration, which most mosques in Europe have been compelled to adopt, that determines the beginning of the month of Ramadan by astronomical calculations, and what is the ruling on whoever follows it?

We have previously clarified the impermissibility of relying on astronomical calculations to determine the beginning and end of lunar months, stating that it is a view contrary to what the authentic hadiths indicate, to what the Companions agreed upon, and it is rejected by the majority of scholars. The Islamic Fiqh Academy has also decided against relying on it. The crescent (hilal) is derived from appearance, and if people do not see it, it is not a crescent, and there is no weight given to the statements of astronomers. Sheikh al-Islam Ibn Taymiyyah mentioned that the crescent is something witnessed and seen with the eyes, and its rising in the sky, if it does not appear on earth, has no legal effect.

Regarding the aforementioned statement, we have several observations: 1. Their statement, "Muslims in European countries must adopt this rule," obliges something that Allah and His Messenger have not obliged. 2. If they believe there is no weight to the اختلاف المطالع (difference in moonrise), why do they not make it obligatory for Muslims all over the world? 3. Their claim that astronomical calculation is definitive is a claim refuted by reality, as there have been multiple instances where astronomers reported the impossibility of sighting, yet it was subsequently confirmed by the testimony of trustworthy witnesses.

In summary, we believe that this statement has no weight, and Muslims in Europe must seek to sight the crescent. If they see it, they fast; and if they do not see it, they complete thirty days of Sha'ban, which is what the Sharia has prescribed.