Which Calendar Should Determine Ramadhaan?
As can be seen, even predetermined calendars which are calculated according to precise measurements require some specific methodology, such as conjunction, moonset-after-sunset, or some other precise measurements. The differing methodologies will result in different calculated calendars.
The question arose among Muslim scholars: should Ramadhaan, and other religious days of fasting/celebration such as the 10th of Muharram [‘Aashuraa’u] and the 10th of Dhul Ḥijjah [Eid al-Adhaa], be determined through actual crescent sightings or a predetermined calendar?
Several scholars argued that dates which have a religious significance should be determined through actual crescent sightings, the way the Prophet Muhammad did, and the calculated calendar can be used for civil purposes. Other scholars posited that a calculated calendar should be used for both civil and religious dates, the same way that it is used by most urban Muslims throughout the world for their prayer times, without having to actually check the light in the horizon for Fajr or the shadow-length for ʿAsr.
Global Sighting vs Local Sighting:
If one region in the world sees the crescent but the other does not, should they adopt the same date or a different date? Muslim scholars have disagreed over this issue because it was not directly addressed by the Prophet. In the past, one city like Makkah may sight the crescent but the Muslims in Damascus do not. News about the sighting would take a long time to travel, and the people of Damascus would have already skipped the first day of fasting, assuming that Ramadhaan had not begun yet.
Therefore, in the past, some Muslim communities would begin and end Ramadhaan on different days. With the advent of modern communications, it seems that this issue has been resolved because one region can instantaneously send a message to another region about purported sightings. Nonetheless, it remains a variable which influences the date of Ramadhaan.
The Hanafiyyah, Maalikiyyah and Hanabillah are of the opinion that the varying horizons should not be considered. If the moon Crescent was sighted in a city, it is an obligation for other Muslims across the globe to commence the fast – because the moon is one and the Prophet said: “start the fast by the sight of the crescent..”. This hadeeth is a general communication to all Muslims across the globe and not specific to certain sect of people. If anyone confirmed the sight of the new crescent, that is the crescent of all others.
The Shaafi’iyyah argued otherwise, and said the varying horizons should be considered. For every nation has its own crescent.
Extracted [Fiqh Ramadhan] page 45, 46 by Ibn Taofeeq Abdul Azeez.