Editing Month (section)

=== Beginning of the lunar month ===
The [[Hellenic calendars]], the [[Hebrew calendar|Hebrew Lunisolar calendar]] and the [[Islamic calendar|Islamic Lunar calendar]] started the month with the first appearance of the thin crescent of the [[new moon]].

However, the motion of the Moon in its [[orbit]] is very complicated and its period is not constant. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore, the beginning and lengths of months defined by observation cannot be accurately predicted.

While some like orthodox Islam and the Jewish [[Karaite (Jewish sect)|Karaites]] still rely on actual moon observations, reliance on [[Islamic calendar#Astronomical considerations|astronomical calculations]] and [[Tabular Islamic calendar|tabular methods]] is increasingly common in practice.<ref>{{Cite web |title=Calculations or Sighting for starting an Islamic month |url=http://www.moonsighting.com/calculation-or-sighting.html |url-status=dead |archive-url=https://web.archive.org/web/20170508214424/http://www.moonsighting.com/calculation-or-sighting.html |archive-date=8 May 2017 |access-date=16 April 2017 |website=www.moonsighting.com |df=dmy-all}}</ref><ref>{{Cite web |last=Chraibi |first=Khalid|date=9 April 2021|language=fr |title=Le mois islamique est-il universel ou national ? |url=http://oumma.com/Le-mois-islamique-est-il-universel |website=Oumma}}</ref>