Should breaking the fast and abstaining in Ramadan be based on the first clearly audible adhan, or on the adhan of the nearest mosque, or on the official state timing, given the variation in adhan times between mosques?

Breaking the fast (Iftar) is at sunset, and abstaining (Imsak) is at dawn, based on the Prophet's (peace be upon him) saying: "When night approaches from this side, and the day departs from this side, and the sun sets, then the fasting person has broken his fast." It is obligatory to ascertain the sunset, as well as the times of the five prayers, by the cosmic signs that the Shariah has made evidence. Whoever does not know the signs may follow a trustworthy muezzin who is knowledgeable of the times. The calendar issued by the Ministry of Endowments or similar bodies should not be relied upon if it is known or highly probable that it contradicts the Shariah signs, or that it is inaccurate. It is unlikely for the time difference in the Maghrib adhan between mosques to reach a quarter of an hour.