Second: Matters related to crescent sighting.
The matters of crescent sighting are not considered new issues in terminological sense because they are found in old times but frequent travels, new airplanes, and new technologies made these issues come out to surface, so it may be described as new issues.
1 - Difference in crescent sighting:
Crescent sighting is of the controversial issues and nobody has questioned that, but the difference among scholars lies whether we should unify the crescent sights or not. The most correct view is to consider the difference in crescent sighting ad each country should see the crescent itself because of the Hadith that was reported in Sahih Muslim from the Hadith of Kurayb that Um Al Fadl, the daughter of Al Harith sent him to Mu`wiyah in the Levant. He said: I (Fadl) arrived in Syria, and did the needful for her. It was there in Syria that the month of Ramadan commenced. I saw the new crescent (of Ramadan) on Friday. I then came back to Medina at the end of the month. Abdullah ibn `Abbas (Allah be pleased with him) asked me (about the new crescent of Ramadan) and said: When did you see it? I said: We saw it on the night of Friday. He said: (Did) you see it yourself? I said: Yes, and the people also saw it and they observed fast and Mu`awiyah also observed fast. Whereupon he said: But we saw it on Saturday night. So we would continue to observe fast till we complete thirty (lasts) or we see it (the new crescent of Shawwal). I said: Is the sighting of the crescent by Mu`awiyah not valid for you? He said: No; this is how the Messenger of Allah (may peace be upon him) has commanded us.
Imam An-Nawawy titled the chapter in which he mentioned this Hadith —in his commentary to Sahih Muslim— with: Each county should have a different crescent sighting and if the crescent is ascertained in a country, it will not be incumbent on a far country.
In case it is permissible for a Muslim to differ in regard of daily fasting and breaking the fast, monthly fasting and breaking the fast is permissible, which is the chosen view of Shaykh Al Islam (may Allah bestow mercy on his soul), Shaykh Ibn Baz, and Shaykh Ibn `Uthaymeen (may Allah bestow mercy on their souls). The international Islamic Fiqh Academy also reached a decision No. (7) at its fourth session in 1401 AH with the same ruling in this regard.
The International Islamic Fiqh Academy also stated that there is no need to call for unifying the crescent sighting and festivals in the Muslim world because unifying them will not be the only thing that guarantees the unity of the Islamic nation as some people think. The only thing that will guarantee the unity of the nation and uniting their word is their agreement on acting according to the Book of Allah and the Sunnah of His Messenger (peace be upon him) in all their affairs.