It is not possible to announce one day as Eid Al-Fiṭr for all Muslim countries, since the announcement of the Eid for each country is based on the sighting of the Moon in that country itself. However, if the Moon is sighted in a city, then the start of the month is also ascertained for nearby cities as well as remote cities which are deemed to share the same horizon, meaning the cities that are not too far from one another. For instance, in Iran, not all cities have a united horizon. However, almost all of the areas in the country fall on similar horizons and if the Moon is sighted in cities located in the center of Iran, its observation can be confirmed in other cities as well. Also, those who live in the Persian Gulf region can act according to the announcement of the beginning of the month in Iran, but those who live in the Western and Eastern countries should act according to the views of trustworthy astronomers from whose statement they can reach certitude. Even neighboring countries such as Afghanistan cannot act according to the announcement of the beginning of the month in Iran unless they are deemed to fall on the same or similar horizon. For example, their horizon is different by 0.5 degrees. One cannot prove that the previous night was the eve of the first day of Shawwal based on the height of the Moon from the horizon and late setting of the Moon. Furthermore, accurate astronomical calculations as well as calendars do not confirm the start of the month unless one can gain confidence in their statements about the sighting of the Moon. Nevertheless, nowadays with respect to the precision of astronomers' equipments, provided that all astronomers reach a consensus on the sighting of the Moon, one can hardly disagree with them unless a large number of people contradict their statements.