Ramadan is the holiest month in the Islamic calendar and fasting during the month is one of the five pillars of the religion.
The Islamic calendar is based on lunar cycles, not the Gregorian calendar, which is why the exact date of Ramadan changes each year.
As the charity Muslim Aid says: "The Islamic calendar follows the phases of the moon, commonly known as the lunar cycle.
"As a result, the Holy month of Ramadan falls approximately 10 days earlier each year in the Gregorian calendar."
Ramadan is the ninth month of the Islamic calendar, and only begins when the new moon is sighted.
It can vary by one day from country to country if the new moon is sighted in one country but not yet in another.
This year it is set to begin on Tuesday April 13.
Ramadan lasts either 29 or 30 days, ending when the next new moon is sighted.
At the end of the month, Muslims celebrate Eid-al-fitr, marking the beginning of the next lunar month.
Ramadan is a special month which commemorates the first revelation given to the Prophet Muhammad.
It is believed that the Quran - the Islamic holy book - was revealed to mankind during Ramadan through the Prophet Muhammad.
During the sacred month, Muslims who are able to fast abstain from food, drink, smoking, and marital relations from dawn until sunset.
They also try to avoid other sinful acts, including gossip and swearing.
It’s not allowed to eat or drink during the hours of daylight, although there are exceptions for those who are ill, travelling, elderly, pregnant, breastfeeding, have a chronic illness, or are on their period.
It is also generally a time of reflection and a period of focusing on faith.
Salman Waqar, from the British Islamic Medical Association (BIMA), said Muslim scholars across the world have said vaccinations do not break the fast and people should not delay their Covid jab on account of Ramadan.
