Answer:
Ibn Umar (Radiyallahu Anhu) narrates that the Messenger (sallallaahu alaihi wa sallam) said, “The months are 29 nights. So do not fast until you see it (the moon). If clouds obscure the view, complete 30 days.” (Bukhari)
Abu Hurairah (Radiyallahu Anhu) narrates that the Messenger (sallallaahu alaihi wa sallam) said, “Commence fasting upon seeing it (the moon) and end fasting upon seeing it (the moon). If clouds obscure the view then complete the number (i.e. 30 days).” (Muslim)
Ibn Abbas (Radiyallahu Anhu) narrates that the Messenger (sallallaahu alaihi wa sallam) said, “Do not fast before Ramadan. Commence fasting upon seeing it (the moon) and end fasting upon seeing it (the moon). If clouds cover it (the moon) then complete 30 days.” (Tirmizi)
The ahaadith above make it clear that even if the moon is present but cannot be seen due to the clouds obscuring the view, one is to complete fasting for 30 days.
Therefore, based on the abovementioned ahadith and the ruling of the jurists, it will not be permissible to base the beginning and end of Ramadan or other Islamic months on calculations.
Living in a technologically advanced era does not justify changing this teaching of Islam.
(Majmu’a Rasa’il al-Laknawi: 2/210-215)
(Raddul Muhtaar: 2/387, Saeed)
Mufti Faizal Riza
10/9/2011