The Islamic calendar is lunar that is based on the moon, unlike the Gregorian calendar followed by the West. Since lunar months are shorter than solar months, Muslims holy month of Ramadan, which takes place in the ninth month of the Islamic year, occurs approximately 11 days earlier every year depending on when the moon is sighted and the same is for Eid which varies from country to country by about a day. While many depend on sighting the crescent moon by the naked eye, some organisations use astronomical charts to plan a long way ahead.

The Saudi Arabia government uses the Umm al-Qura Calendar which is determined at the Institute of Astronomical & Geophysical Research of the King Abdulaziz City for Science and Technology (KACST) in Riyadh. Although this calendar is often criticised by other Muslim organisations and communities who depend on the actual sighting of the lunar crescent, it is followed by several neighbouring states on the Arabian Peninsula such as Bahrain and Qatar apart from the Islamic Society of North America (ISNA), the Fiqh Council of North America (FCNA) and the European Council for Fatwa and Research (ECFR).

Eid-ul-Fitr in UK
Expecting Eid to take place on Tuesday, June 4 or Wednesday, June 5, the Green Lane Masjid and Community Centre in Birmingham has announced that its annual Celebrate Eid event will be subject to the moon. As per a UK Government agency, HM Nautical Almanac Office, the new moon happens on Monday, June 3, 2019, at 10:02 UT / 11:02 BST. Hence, under excellent conditions, moon sighting is possible on June 3 through the naked-eye, from the islands such as the Kiribati Republic and Samoa.

While the northern half of UK is predicted to wait until Wednesday, June 5 for sighting the crescent moon, the southern half of the United Kingdom along with the Middle East and North Africa are expected to sight the moon on Tuesday, June 4.

Eid-ul-Fitr in Morroco
In Morroco, Eid-ul-Fitr is expected to be on June 5. According to the forecast, the moon is not likely to be sighted on Monday, June 3, the 29th day of Ramadan which means that it should be easily visible on the evening of the 30th day of Ramadan which is on Tuesday, June 4. Hence, Eid al-Fitr in Morroco is likely to be on Wednesday, June 5.