The preferred opinion among all the schools of Islamic Fiqh has been that the month of Ramadan cannot be determined by the calculations.
Astronomical calculations, in view of the majority of Jurists, rest on mere assumptions and are hypothetical in nature.
Therefore, significant acts of worship such as beginning and ending of the month of Ramadan cannot be based on probabilities and uncertain presumptions.
Consequently, the months connected with acts of Islamic Ibadat such as Ramadan, Shawwal or Zil-Hajjah, can only be determined either by practical sighting (الرُّؤْيَةِ) or by completion
