French Muslims split over start of Ramadan despite accord PARIS (Reuters) - An agreement in France to set the start of Ramadan according to scientific calculations fell apart on Tuesday when many mosques opted to wait as the new moon was not yet visible to the naked eye there or in the Middle East. The Islamic lunar calendar is 10 to 11 days shorter than the solar Gregorian one developed in Europe, so the Muslim holy month starts a week and a half earlier each year, when a new crescent moon is seen. As that can happen on different nights in different parts of the world, Muslim leaders in France agreed in May to break with tradition and use scientific methods to determine when the new moon appears, setting Tuesday as the first day of Ramadan. But Muslim groups in northern Paris suburbs and the city of Lyon said on Monday they would wait until Wednesday to start fasting after they failed to sight the new moon by traditional direct observation and Saudi, Egyptian and North African Islamic authorities reported the same problem. The Paris Grand Mosque, which had planned to start Ramadan on Tuesday, as determined by the astronomers, switched to Wednesday after those Muslim countries and several French Muslim groups announced they would start the dawn-to-dusk fasting that day. Other Muslim groups stuck to the agreement to start Ramadan on Tuesday, causing confusion among France's 5 million Muslims. "This is something really important, it's one of the pillars of Islam, and it's forbidden to mess around with that," Oualid Beliouze said at the Paris Grand Mosque where he went after hearing about the confusion on the radio. Turkey began using scientific calculations to set the start of Ramadan decades ago. Muslims in Germany, who are mostly of Turkish origin, and those in Bosnia do the same. Muslim minorities elsewhere in Europe often start Ramadan according to its beginning in their countries of origin, or in Saudi Arabia. That can lead to different ethnic groups starting it on different days, even in the same country. Additional reporting by Pauline Mevel; Editing by Robin Pomeroy