In the Hanbali school, there is no valid opinion that permits astronomical calculation as method for establishing Ramadan, even for the sake of unifying the Ummah or making scheduling easier.

If the horizon is blocked by clouds or similar obstruction on the 30th night of Shaʿbān, the following day is fasted with the intention that it is Ramaḍān, as a precaution.

Outstanding Ramaḍān fasts must be made up in Shaʿbān when delaying would carry them into the next Ramaḍān.