Middle-East Journal of Scientific Research 22 (1): 115-120, 2014 ISSN 1990-9233 © IDOSI Publications, 2014 DOI: 10.5829/idosi.mejsr.2014.22.01.21831 Corresponding Author: Abdul Halim Abdul Aziz, School of Physics, Universiti Sains Malaysia, 11800 USM Pulau Pinang, Malaysia. 115 A Unified Islamic Calendar Proposal for the World Abdul Halim Abdul Aziz and Ahmed Kamil Ahmed 1 2 School of Physics, Universiti Sains Malaysia, 11800 USM Pulau Pinang, Malaysia 1 Department of Astronomy and Space, College of Science, University of Baghdad, Baghdad, Iraq 2 Abstract: To date, there is no single global Islamic calendar for the community. Over the years, the computation of the Islamic calendar has become a subject of much debate. In this paper, we propose a unified global Islamic calendar (UGIC) based in the concept of “expected visibility”, International Dateline and a single calendar for the whole world. We used a new sightability criterion to determine young crescent visibility that is based on eye-detectable contrast between the crescent illumination and sky background. We propose an unconventional reference for calendar construction that is based on a line instead of a point. We embraced the International Date Line as day (and month) separator. A three-year calendar has been produced based on the above method for evaluation. Key words: Islamic Calendar Unified Islamic Calendar Time-keeping INTRODUCTION systematic pattern of predictability when a uniform Apart from the Gregorian calendar, which serves as calendar. an international standard for civil time keeping, there are Most often in astronomy the instance of lunar other calendars that are used for religious and cultural conjunction is referred to as new moon. In the Islamic purposes. Unlike the Gregorian calendar, which is tradition, however, a new moon is only recognized after Solar-based, most others are lunar based, either purely the first eye-sighting of a thin lunar crescent at the time lunar or luni-solar. The Islamic calendar is a purely lunar of local sunset and, of course, before the moonset and calendar. Islamic year consists of 12 lunar months without after lunar conjunction. This usually happens leap months. The lunar months are: Muharram, Safar, approximately 12-30 hours after a lunar conjunction. In Rabiulawal, Rabiulakhir, Jamadilawal, Jamadilakhir, recent decade eye-sighting has included optically aided Rejab, Syaaban, Ramadan, Syawal, Zulkaedah and sighting. However, the actual crescent sightability of Zulhijjah respectively. The Islamic lunar calendar the new month cannot be predicted precisely because it involves the astronomy of new moon’s earliest depended on atmospheric conditions that accompany visibility on local, regional and global scales [1]. It is a the sighting [3]. Hence, the central problem in preparing widely used time system. However, it has remained a the Islamic calendar (in advance) is to formulate localised system, with each region or country applying computational procedures for determining the youngest localised calculations and/or sightings. The methods visible phase of the crescent [4]. For computing a global of determining the crescent sightability also vary calendar these computations must then be applied to an from region to region, resulting in a calendar that is agreed reference place on the surface of the Earth. not uniform on a global scale. The need for a global Traditionally, crescent visibility is important to a Islamic calendar is a requirement of modern times in muslim society for determining the beginnings of special response to rapid transportation and communication. lunar months, which are Ramadan, Syawal and Zulhijjah. In recent decades serious attempts have been made Crescent sighting activities are carried out on the 29 day towards globalising the Islamic calendar by scholars of the previous month. It is more involved than just like Ilyas [2]. Following his critical appraisal of the computing the times of conjunctions. There are several lunar visibility (prediction) criterion he went on to reasons that affect the new moon visibility. They can be study its impact over the entire globe and discovered a divided into two categories: criterion is applied. This paved way for a unified th