This evening marks the beginning of the holy month of Ramadan, the annual occasion for Muslims to celebrate the first revelation of the Quran to the Prophet Mohammed.

Here are seven things you should know about it.

1. This year Ramadan begins this evening, May 26 and will run for 30 days until the evening of June 24. However this month, the ninth of the Islamic calendar, moves around every year according to the lunar cycle. It begins with the sighting of the crescent moon, and the first day of fasting will begin tomorrow at sunrise.

2. It's a fast, from several things. Observant Muslims don't eat or drink in daylight hours during Ramadan. Coffee, tea, or anything containing caffeine is disallowed, as are fizzy drinks, tobacco and sexual intercourse.

3. Fasting is one of the 'Five Pillars' of Islam, the others being the shahadah, the declaration of faith; salat, the five daily prayers; zakat, or almsgiving; and the hajj, the pilgrimage to Mecca.

4. Some are exempt from the fast. This includes most children before they reach puberty, elderly people and the sick, travellers and women who are breastfeeding or menstruating. Those unable to fast are encouraged to instead feed a needy person for every day they are not fasting.

5. It's not just about giving things up. For many it's also a time to recharge spiritually, draw closer to Allah in prayer, read the Quran and practise giving generously to charity. Islamic aid charities will often run appeals at this time of year.

6. The fast breaks at sundown. At sundown every day, known as 'iftar', the fast is broken. Families will share evening prayers before having a meal together. Another meal called the 'suhoor' takes place in the morning just before dawn, and then fasting resumes.

7. The fast ends with the festival of Eid al-Fitr, which is celebrated with gifts to charity and to one another, visits and parties. 'Eid Mubarak' – 'Happy Eid' is a common greeting.