MUHAMMADIYAH.OR.ID, YOGYAKARTA—Oman Fathurrahman, a Muhammadiyah astronomer, mentioned five principles of the global Islamic calendar.
First, the global Islamic calendar uses the method of hisab (an astronomical calculation). It is similar to the use of hisab to determine prayer time. The hisab method refuses the rukyat (moon sighting) method.
Second, there should be a transfer of imkan rukyat. The crescent moon cannot be sighted all around the world concurrently. The crescent moon may be visible in several parts of the earth, and it is enough to indicate that the new moon has begun worldwide.
“Imkan rukyat in a place represents other places where it has not occurred yet. However, it cannot be applied the other way around,” said Oman.
Third, the earth is seen as one matlak. It is a consequence of transferring imkanu rukyat. Therefore, imkanu rukyat in a place applies to all areas because the earth is viewed as one matlak. It also means a refusal of the principle of different matlak.
Fourth, the global Islamic calendar applied a global convention on day transition. It occurs at midnight or 00:00, and the progression of days proceeds from east to west. A day encompasses the time span from 00:00 to the subsequent 00:00, encompassing 24 hours.
Last, the global Islamic calendar shows the International Date Line (IDL) acceptance. Oman said accepting the IDL involves acknowledging and utilizing the internationally recognized designated line for day transitions. The IDL serves as the dividing point for the commencement of a new day. For instance, if it is Sunday on the east side of the line, it will be Monday on the west side.