A Suggested Global Islamic Calendar based on Imkan-e-Ru'yah (sighting possibility) somewhere in the world is that if the moon is born before 12:00 UT [23:59 or less of the previous day at International Date Line (IDL)], then the month begins at sunset of that day everywhere in the world. If the moon is born after 12:00 UT, then the month begins on the next day's sunset everywhere. IDL has been universally accepted even by Muslims as the beginning of every day of the week. All Muslims pray Friday prayers on the same day starting at IDL. Global Islamic Calendar should also follow the same convention of the day, so that the whole world can start Ramadan or Eid on the same day.
The moon born before 12:00 UT has Imkaan-e-Ru'yah somewhere on earth, and the moon is born before the day begins at IDL, so the whole world can start the month on the same day. This suggested Global Islamic Calendar is so easy to calculate for any ordinary Muslsim that no expertise of astronomy or science is required. All that is needed is Conjunction time which is easily available from many sources on the Internet. This suggested Global Islamic Calendar was also discussed at 1st Global Calendar Meeting in Morocco, November 2006 attended by representatives from various Islamic countries. People started understanding the importance of Global Islamic Calendar. See one web site "Time & Strategy".