Must Muslims in France fast and break their fast according to the sighting in Saudi Arabia or France? And why does the Day of Arafat differ between countries despite it being the standing of pilgrims on Mount Arafat?

Scholars have differed on the issue of sighting the crescent moon: Is the sighting of the crescent moon in one country binding on all other countries, or does each country have its own sighting? The majority of scholars lean towards the first opinion, while Imam Al-Shafi'i, in his later opinion, leaned towards the second, which states that each country has its own sighting. This is also the view preferred by some fatwas.

If the sighting of the crescent moon is confirmed in one country, it is not permissible to disregard its sighting.

The criterion is not solely the sighting of the crescent moon in Saudi Arabia. Rather, for those who believe that the sighting in one country applies to all, the crescent moon must be sighted in any country.

Most countries follow the Kingdom of Saudi Arabia regarding the crescent moon of Dhul-Hijjah due to the connection with the holy sites.

This is a matter of ijtihad (independent juristic reasoning), and scholars hold two opinions on it. There is no blame on whoever acts according to one of them, whether through ijtihad or permissible taqleed (following a qualified scholar). It is not permissible for anyone to condemn those who differ with them. However, it is preferable not to overtly display disagreement with the general populace regarding fasting and breaking the fast, out of concern for not widening the scope of discord among Muslims.

Whoever fasts based on a sighting outside their own country and then breaks their fast with their own country is contradicting themselves, as both issues are intrinsically linked.

There is no blame on whoever acts according to the sighting of the crescent moon if it appears in a country other than their own, which is an opinion held by a large group of scholars. However, they should not openly express their disagreement with the people, as this can cause discord.

If the people of a country search for the crescent moon but do not see it, and people act accordingly, disregarding the sighting of other countries, this is also an opinion held by a large group of scholars.

Ultimately, this is a matter of ijtihad. There is no blame on whoever acts according to either of the two opinions, and it is not permissible to condemn them. It is important to avoid displaying disagreement among people to preserve the unity of Muslims.