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.id al-Adha in 2016 is on Sunday, the 11th of September. Based on sightability in. , in 2016 Eid al-Adha will start in North America a day later-on Monday, the 12th of September.