A Student Asked Me, After I Said We Are Now in Autumn, Why I Had Written the Month - Jurisprudential Answers - Miscellaneous Issues, Vol 5

Ahmed al-Hasan Response:

This concerns the Hijri lunar calendar, which is a dating system that the Messenger of Allah did not establish, so it cannot be held against the Islamic religion. In the time of the Messenger Muhammad, the Hebrew lunisolar calendar that the Arabs had taken from the Jews was in use. According to that calendar, there would not be a problem with the month of Rabi corresponding to the actual spring in most countries of the world, because the shortfall in the lunar year is added so that it corresponds with the solar year.