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 calendar is an intensely scientific system, critically involving the astronomy of the new Moon's earliest visibility on local, regional and global scales. During the last 15 years, the astronomical prediction of the new Moon's visibility and its use in a unified International Islamic Calendar 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 underlying this issues. It also highlights how seemingly erroneous reports of Moon sightings complicate the resolution of this issue and the utility of the criterion in discerning the sighting reports. Finally, by re-analysing data it is shown that a composite criterion and a set of derived simplified criteria provide a good starting basis for a unified International Islamic Calendar.