Today (as I write, March 31, 2013) is Easter Sunday. Worldwide, Christians today are commemorating the resurrection of Jesus Christ (traditionally believed to have occurred on a Sunday).

On the calendar, Easter Sunday falls in close proximity each year to the Jewish holiday of Pesach or Passover (the Last Supper may have been a Passover seder meal). And, like Passover, this major Christian holiday does not fall upon the same date each year. In other words, just because Easter happens to be on March 31 this year (2013) doesn’t mean that it’s always on March 31.

Last year, for instance, Easter was April 8, 2012; next year, by contrast, Easter will be April 20. Why does Easter fall upon different dates in different years? Put simply, because Easter is always the Sunday after the first full moon on or after March 21 (approximately the vernal or spring equinox in the northern hemisphere), which of course can and does vary each year.

This means that Easter Sunday may fall anywhere between late March and mid-to-late April.

Additionally, the matter of determining the date of Easter Sunday each year is complicated further by the fact that different branches of Christianity utilize entirely different calendars in order to do so. Catholics and Protestants use the Gregorian (Western) calendar to identify March 21; Eastern Orthodox churches, by contrast, rely instead upon the rather different Julian calendar, whose own March 21 usually falls on a different actual date than that of the Gregorian calendar’s March 21.

Depending upon the year, the Eastern Easter can be on the same date as the Western Easter, or as much as over a month later.

The precise year in which the crucifixion and death of Jesus occurred is uncertain, but is estimated by many to have been circa 33 AD (or 33 CE).

The traditional Christian religious view is that Jesus Christ, understood by Christians to be the Son of God and a divine Savior, voluntarily died a self-sacrificial death in order to pay for, or atone for, all human sin. The New Testament gospel accounts paint a picture of Jerusalem’s Jewish leaders sentencing Jesus to death for the religious crime of blasphemy (for claiming to be divine).

Secular historians, by contrast, tend instead to view Jesus’s execution primarily as inflicted upon him by Jerusalem’s Roman overlords for the capital political crimes of treason and sedition. Death by crucifixion was Rome’s standard, and deliberately tortuous and humiliating, means of ridding itself of (and making examples of) troublesome political enemies and potential rabble-rousers — which is essentially how the Roman authorities viewed Jesus.

A traditionally somewhat joyous holiday characterized by themes of triumph and renewal, Christians observe Easter Sunday in various ways, which may include prayer, special church services, family meals, and — of course — the traditional colorful decorating of Easter eggs, and subsequent Easter egg hunts.

So, to all my Christian friends and readers, may I wish you all a Happy Easter!