A ROBUST UNIFIED ISLAMIC CALENDAR PROPOSAL FOR THE WORLD

Abstract

To date, there is no single global Islamic calendar that is in use for the community. The computation of the Islamic calendar has become a subject of discussion. In this paper, we propose a Unified  Global  Islamic Calendar (UGIC) based on expected visibility of the youngest crescent moon, the International Dateline, the global lunar visibility curves and a single calendar for the whole world. Two different visibility criteria were applied to two regions of the globe. An unconventional visibility test is proposed that  is based on  a line  instead of a point on the globe. A topocentric crescent illumination threshold criterion of 0.52% at local sunset is set for the Western region and tested at longitude 60^o W along a line between latitudes ±20^o. A second test criterion is based on the lunar conjunction event that has to occur before local sunset at any point on the globe.  This criterion is applied at the Eastern extreme, longitude of 180^o E, and tested along a line between latitudes 15^o N and 35^o S.  We  embrace the International Date Line as a day separator, and UTC as the standard clock. A 515 year calendar has been generated and tested for robustness. A 12-year  calendar is produced based on  the above method.