Accordinf According to the standard narrative, Ramadan had always coincided with the Advent Fast and Eid ulAzhar had always coincided with Palm Sunday until 632. But following 12 Lunar Months the calendar had slipped forward two whole months against the Solar year by the time Umar's came to power in 634.
Some of the Saracen leaders mentioned during Umar's name are referred to by similar names such as Amr. The standard narrative is that they represent different people but it might not necessarily be the historical case.