Answered by Shaykh Faraz Rabbani
If someone is keeping an optional fast then do they have to open it as soon as maghrib starts or can they delay it for as long as they like. and also what happens if you fell asleep after asr and woke up well after maghrib had started? should one remake that fast or will he be forgiven.
Answer:
Walaikum assalam wa rahmatullah,
It is recommended, not obligatory, to break any fast quickly after Maghrib has entered. [Ala’ al-Din Abidin, Hadiyya al-Ala’iyya]
As such, you could delay breaking your fast without being sinful. However, doing so unduly without excuse is disliked.
Wassalam,
Faraz Rabbani