LUNAR CRESCENT VISIBILITY CRITERION AND ISLAMIC CALENDAR

While the Islamic legal system dictates the general considerations for an Islamic timekeeping system, it is science which is called upon to assist in safeguarding these legal precepts. The Islamic lunar calenda r is an intensely scientific system, critically involving the astronom y of the new Moon's earliest visibility on local, regional and global scales. During the last 15 years, the astronomical prediction of the n ew Moon's visibility and its use in a unified International Islamic Ca lendar has received considerable global attention. Within the religio- legal system, there are important considerations which may help in the simplification of this exercise and which need to be kept in view by scientists. This paper aims to review the developments in the area of a prediction 'criterion' as well as the 'legalistic' aspects underlyin g this issues. It also highlights how seemingly erroneous reports of M oon sightings complicate the resolution of this issue and the utility of the criterion in discerning the sighting reports. Finally, by re-an alysing data it is shown that a composite criterion and a set of deriv ed simplified criteria provide a good starting basis for a unified Int ernational Islamic Calendar.