The rules of Islamic Shariah should be drawn from Quran and Sunnah.
The so called 'Imkaane ru'uya' has no basis in Quran and sunnah. It is based on the common belief that Islamic months begin after people see the new crescent in the west.
Even though this has been the common practice of the people, it is a BID'AH which was not practiced by the Prophet (Peace Be Upon Him) and the Sahaba (RA). We must be very careful with BID'AH because it ultimately leads one to the hell.
The scientific caculations to find out the place where the new crescent will be seen was initiated by non-muslims. The Aalims without proper knowledge on Astronomy told the non muslim scientists that the Islamic months begin after the Hilaal is sighted. The Aalims had no reason to doubt about it because it has become the order of the day. People believed that the earth was flat and Hilaal will be visible eveywhere alike.
So, the scientists with a view to help the muslims find out the day on which the Hilaal would be visible created the visibility curves and the Muslims believed that it would be better than naked eye sighting, which always created confusion.
Visibiliy of Hilaal is different from place to place just as our prayer times. So, people believed that beginning of fasting also must be different. For them it was the sighting of the Hilaal which informed the change of month. Thus in the age of meagre communication facilities people did things depend! ing on the local visibility of the Hilaal.
All people, illiterate as well as literate believed firmly that Ramadan begins after seeing the new crescent.The people who could understand Quran and Hadees were very few and they too did not want to disturb the established order. This practice began to get a scientific tint and now even the educated people firmly believe that the month should not begin without the possibility of visibility. Astronomers were very well aware that hilaal will be visible only after sunset on the first day.
Now the scientific visibility and the true method of observation still in vogue at some places began to contradict because;Hilaal is not the criterion of fixing the months. This is how the scientists and common people began to differ in the hilaal.
In Haramain where Islam originated the months begin one or two days earlier than other places in the world. This is because the real method was practiced in Haramain (till recent past) while at other places people begin the month only after sighting the Hilaal.
Now to solve this problem of descrepancy of dates in Islamic towns a study must be conducted and the Ulema and the leaders must arrive at a concensus in this issue. The solution to this lies in establishing the Islamic calendar and practicing it all over the world together with the conventional calendar.