What are the reasons for the Muslims' disunity in determining the day of Eid al-Fitr, and is disagreement permissible in this matter?

The disagreement regarding the sighting of the Shawwal crescent in France and elsewhere reflects an old scholarly dispute, and it is among the issues where disagreement is permissible. It should not be a cause for division among Muslims. This disagreement is a mercy and an expansion for the servants. Scholars have clarified that such matters of ijtihad (independent reasoning) should not be condemned by force, and no one has the right to compel people to follow them. Rather, they should be presented with scientific arguments, and there is no blame on whoever adopts one of the two opinions, while respecting the opinion of others.