The Duty of One in Yawm al-Shak
Issue No. 1332- If there is a doubt about the last day of Sha’ban or the first day of the month of Ramadan, the fast of that day is not obligatory. If however, somebody wants to observe fast on that day, he should observe the fast with the intention of the last day of Sha’ban, or if he has qaḍā fasts due to be performed, he should make the intention of qaḍā. If it transpires later that it has been the holy month of Ramadan, it will be considered as the fast of the month of Ramadan. If however, he realizes during the day that it is the first day of Ramadan, he should immediately switch his intention to the fast of the month of Ramadan.
