At what distance does the lunar horizon (matla') change?

Question

According to the Shari'a, cities situated at what distance are regarded as having one lunar horizon (matla'), and at what distance does the matla' change? Please explain the matter fully. If two cities or countries have one matla' and the news of the sighting is correct, can the people of the other city begin fasting or celebrate 'Id on the report of that sighting or not? If at some time a false report of a sighting was broadcast from somewhere, will news of a sighting from there never be accepted again?

Answer

At a distance of a thousand miles the matla' changes. If the sighting is established in the Shari'a way, the ruling of fasting and 'Id will apply; otherwise not. The almanacs and calendars themselves differ among one another: nowadays almanacs are generally not compiled by observing sunrise and sunset and studying them systematically (istiqra')

Source: Fatawa Mahmudiyya

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