In the Muslim calander, a holiday begins on the sunset of the previous day, so observing Muslims will celebrate Eid al-Adha on the sunset of Sunday, the 7th of December.
Although Eid al-Adha is always on the same day of the Islamic calendar, the date on the Gregorian calendar varies from year to year, since the Gregorian calendar is a solar calendar and the Islamic calendar is a lunar calendar. This difference means Eid al-Adha moves in the Gregorian calendar approximately 11 days every year. The date of Eid al-Adha may also vary from country to country depending on whether the moon has been sighted or not.
