Moon phases and predicting Ramadan dates

Find out how astronomers use the phases of the Moon to predict the dates for Ramadan each year. Watch the video below with Royal Observatory astronomer Hannah Banyard and New Crescent Society founder Imad Ahmed.

Dates of Al Hijra in western calendar

Al Hijra is the first day of the Islamic New Year and of the Islamic month of Muharram. It marks the day when Mohammed began his migration (Hijra, هِجْرَة) from Mecca to Medina in Islamic Year 1 (1 AH), 622 CE. Ras al-Sana (رأس السنة ) is the Islamic celebration of the new Hijri year.

• 2021 (1443 AH): 9 August

NB future dates are estimates and depend on first sightings of the crescent moon.

The Islamic (Hijri) calendar

The Islamic calendar is a classic lunar calendar consisting of 12 synodic (lunar) months, each of 29.5 days, giving a year of 354 days. It is 11.25 days shorter than the tropical year.

Each month starts with the first naked-eye sighting of the crescent Moon (Hilal). Since this depends on a variety of factors printed calendars are based on estimates of the sighting.

The years are numbered with Islamic Year 1 corresponding to 622 CE.

Not all Islamic countries use the first sighting of the crescent Moon to signal the start of the month. In Saudi Arabia and Egypt the beginning of the month is fixed by the relative timing of sunset and moonset on the 29th day of each month. If the Moon sets before the Sun the next day is the 30th of the month. If the Sun sets before the Moon (by at least 10 minutes in Egypt) the next day is the first of the next month.

Months of the Islamic calendar

*Zul Hijja has 30 days in a leap year.

Previous events

Eid 2019

The date for Eid al-Fitr (Festival of Breaking the Fast) and the start of each new Islamic month depend on the sighting of the new crescent Moon. On 4 June 2019, we broadcasted a live moonsighting on Facebook to mark the end of Ramadan with Royal Observatory Astronomers Brendan Owens, Dr. Emily Drabek-Maunder, Tom Kerss and guest amateur astronomer, Imad Ahmed, from The New Crescent Society.

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Ramadan 2018

The dates of Ramadan and other Islamic months depend on the sighting of the new crescent Moon. On 16 May 2018, we broadcasted a live moonsighting on Facebook for Ramadan with Royal Observatory Astronomers Brendan Owens and Tom Kerss and guest amateur astronomer, Imad Ahmed, from The New Crescent Society.

Calendars from around the world

The Museum's e-book Calendars from around the world, written by Alan Longstaff, informed some of the text of this article.