Q. As Muslims (Sunni) why is it for the commencement of the Month of Ramadan we only start fasting with the actual sighting of the moon, BUT for the breaking of the fast we do not physically rely on the actual setting of the sun; we use calculations for the breaking of the fast.
A. Each Islamic month commences with the sighting of the moon. Calculations are also given with respect to how old the crescent will be, so that it can actually be sighted. These calculations may be used as a form of aid and assistance, however, the actual sighting must be done since this has been mandated in the hadith of the Prophet (S.A).
With respect to breaking the fast, the law of the Holy Quran is that it is broken as soon as the night enters, and the since the night enters with the setting of the sun, and so at this time people break their fast at this time.
Although people still rely on the actual setting of the sun, and they look to ensure that it has set, the times that have been given as calculations do co-inside with the actual setting. In fact, it is on account of the actual setting, the times have been given. So, in reality, Muslims do not rely only on calculations to break the fast, but seeing that the calculated time coincides with the actual setting of the sun, they normally use the time, instead of physically looking at the sun in the Horizon.
And Allah knows best.
Mufti Waseem Khan