The first day of fasting will be on Thursday for many people across the world according to reports.

Judging the start of Ramadan can be a challenge. The Islamic months are based on a lunar calendar, which means that the commencing day shifts earlier every year by approximately 11 days, beginning and ending on a different date.

After a new, waxing crescent moon, a shaving known as a "Hilal" appears at night signifying the first day of Ramadan.

Whilst others defer to the authority of a moon-sighting committee, some Muslims observe the moon locally.

The Gulf News reports, “The Supreme Court of Saudi Arabia has asked its citizens to keep an eye out for the crescent moon on Tuesday, which, if sighted, will mark the beginning of the month of Ramadan on Wednesday.

“If the Ramadan moon is not sighted on Tuesday, the month of fasting will begin on Thursday.”

Astronomical calculations suggest Ramadan will commence on 18 June, 2015 and continue for 30 days until 17 July.

The estimated published dates though, were Morocco - 17 June to 17 July and Egypt/ Saudi Arabia/ Pakistan/ Turkey- 18 June to 17 July.

Yet, according to Morocco World News Ramadan will start in the country on either June 18 or 19, 2015.

An meteorological department official in Karachi said that there were less chances of sighting the moon of the holy month of Ramadan on June 17, adding that it was expected that the moon could be sighted on June 18.