As the lights around the world switched on, it’s time for Ramadan to begin, with the holy month of daily fasting being significantly earlier this year.

The exact start date couldn’t be confirmed too far ahead, because of its dependence on the sighting of the moon. In the UK, astronomers have suggested that the moon will not be visible to the naked eye in Mecca on February 17 – with forecasters believing that the crescent is likely to be more visible across Saudi Arabia on Wednesday February 18.

It means that following officially confirmed in Oman, Ramadan is likely to start on Thursday February 19. However, depending on sightings, it could begin on Friday February 19 for some countries.

Some Muslims in the UK look for the moon in the sky above - meaning that the dates observed can differ not only across the world, but also within the UK. One moonsighting expert, Dr Raja Zahid Nawaz said: "As Ramadan approaches once again, so too does a familiar and frustrating cycle: premature announcements, questionable crescent claims and media outlets repeating statements that simply do not withstand scrutiny.

"The start of the Islamic month is not guesswork. It is not sentiment. And it should certainly not be shaped by convenience."

Dates in Saudi Arabia are calculated by the Institute of Astronomical and Geophysical Research in Riyadh and also used by nearby states, including Bahrain and Qatar, as well as some Islamic councils overseas, such as in North America. Other countries either carry out their own moonsighting, rely solely on lunar forecasts or wait for a declaration from elsewhere.

Ramadan lasts for 29 to 30 days and Muslims observing the fast will refrain from eating and drinking from dawn to dusk so they can focus on prayers, religious study, spiritual reflection and acts of charity instead. Each morning, worshippers eat a nutritious meal called sehri or suhoor to keep them going all day and then, at night, the fasting ends with an evening feast called iftar to replenish the body.

Eid ul-Fitr is expected around Thursday March 19 to Friday March 20, depending on moon sightings.