It is unclear when the first Easter was held but the earliest allusion to the custom of Holy Week, which starts on Palm Sunday and ends with Easter, comes from the Apostolic Constitutions in the latter half of the 3rd century and 4th century from Syria. The author(s) of the Apostolic Constitutions is unknown, but the work claims to have been written by the Twelve Apostles. However, just like the gospels, it was common in ancient times to remain anonymous and attribute work to historical figures, writes Religion Online.