When is the doubtful day and what is the ruling of fasting on the said day?
Yawm al-shakk (doubtful day) means the 30th of Sha’aban. This is because, if the new moon is not sighted, the people are in doubt whether it is still in the month of Sha’aban or already Ramadhan. So, it is prohibited to fast on that day. In fact, it is still considered the month of Sha’aban.