Can I break my fast before I hear the adhān?

The criterion is in the fasting verse itself: “It has been made permissible for you the night preceding fasting to go to your wives for sexual relations. They are a clothing for you and you are a clothing for them. Allah knows that you used to deceive yourselves, so He accepted your repentance and forgave you. So now, have relations with them and seek that which Allah has decreed for you i.e., offspring. And eat and drink until the white thread of dawn becomes distinct to you from the black thread of night. Then complete the fast until the night i.e., sunset. And do not have relations with them as long as you are staying for worship in the mosques. These are the limits set by Allah, so do not approach them. Thus does Allah make clear His verses i.e., ordinances to the people that they may become righteous.” (Qur’an 2:187)

The boundary is the coming of night. The Maghrib adhān is called *because* the sun has set; it is the announcement, not the fact.

In practice this matters more than it seems:

• If you are somewhere with no mosque, or hear no call at all, you break the fast by the timetable or by observation. There is nothing to wait for.
• If the timetable and the adhān differ by a few seconds, what counts is the setting of the sun.
• If you are on a plane and the sun is still visible from that altitude, the fast is not broken until it sets where you actually are.

What is recommended is not to get ahead of it. Breaking the fast promptly once sunset is confirmed is what is praised; doing it on optimistic arithmetic before it has happened would invalidate the day and require making it up.

And a note on the other end of the day, which causes the same confusion: the fast begins at true dawn, not at the Fajr adhān. If you are eating and the call sounds, most scholars say to finish what is in your mouth and carry on fasting as normal.