What should be done if there is confusion about the beginning of the month?

Ahmad said: “If there is confusion about the beginning of the month, one should fast for three days, to be sure of fasting on the ninth and tenth days.” (al-Mughni by Ibn Qudaamah, part 3 – al-Siyaam – Siyaam ‘Aashooraa’).

If a person does not know when Muharram began, and he wants to be sure of fasting on the tenth, he should assume that Dhoo’l-Hijjah was thirty days – as is the usual rule – and should fast on the ninth and tenth. Whoever wants to be sure of fasting the ninth as well should fast the eight, ninth and tenth (then if Dhoo’l-Hijjah was twenty-nine days, he can be sure of having fasted Taasoo’aa’ and ‘Aashooraa’). 

 

But given that fasting on ‘Aashooraa’ is mustahabb rather than waajib, people are not commanded to look for the crescent of the new moon of Muharram as they are to do in the case of Ramadaan and Shawwaal.