As a child, it was very difficult for me to try to explain, and have my friends understand, why I wasn't celebrating Easter on the same day they were observing the religious holiday. I'll do that here with some history included. But first, Happy Easter to the rest of the Christian world on Sunday, April 1, and a Happy Passover to our Jewish faithful around the globe!

I refer to Easter as Pascha or Resurrection Sunday, celebrating the resurrection of Jesus Christ from the dead, as described in the New Testament, having occurred on the third day after his crucifixion by the Romans at Calvary in 30 AD.

Since Easter is a movable feast for all faiths who observe it, the big difference comes within Christianity itself, between the Eastern and the Western Christian faiths. I am an Eastern Orthodox Christian. The formula of calculating what day Easter falls on in Eastern Christianity is based on the Julian calendar, the original calendar of the early church. The rest of Christianity uses the Gregorian calendar. There is a thirteen-day difference between the two calendars, the Julian calendar being thirteen (13) days behind the Gregorian.

The other factor at work is that the Orthodox Church continues to adhere to the rule set forth by the First Ecumenical Council, held in Nicea in 325 A.D., that requires that Pascha must take place after the Jewish Passover in order to maintain the Biblical sequence of Christ’s Passion. The rest of Christianity disregards this requirement, which means that on occasion, Western Easter takes place either before or during the Jewish Passover.

In the meantime, the Eastern Orthodox formula is this: Pascha is to be celebrated on the first Sunday, after the first full moon, following the vernal equinox, but always after Jewish Passover. In order to ensure that there was no confusion as to when the vernal equinox occurred, the date of the vernal equinox was set to be March 21 (April 3 on the Julian Calendar). This formula was universally accepted by all of Christianity, ensuring that Pascha was celebrated on the same day throughout the world.

The Orthodox Church continues to follow this formula exactly as prescribed by the Council of Nicea. Western Christians had this changed by Pope Gregory XIII in 1582 when he corrected the Julian calendar, and it's been a disagreement between the East and the West since then.

Once in a great while, Easter falls on the same day, like last year in 2017, but the next time we'll be celebrating Easter together won't be until 2034.

Until then, folks like me will just have to accept 80 percent off on all after Easter chocolate!

Phil Paleologos is the host of The Phil Paleologos Show on 1420 WBSM New Bedford. He can be heard weekdays from 6 a.m. to 10 a.m. Contact him at phil@wbsm.com and follow him on Twitter @PhilPaleologos. The opinions expressed in this commentary are solely those of the author.