Traditionally, Easter is observed on the first Sunday after the first full moon of spring. Photo by Rick Racela.

The first full moon of spring is sometimes referred to as the Paschal full moon. Traditionally, Easter is observed on the first Sunday after the first full moon of spring.

The vernal equinox (Latin for "equal night") occurred on March 20th. This marks the first day of spring, where daylight and night are both equal.

The first full moon of spring occurred the day after, Friday March 21st. That means Easter will be observed the next Sunday, which is March 23rd.

The last time that Easter fell this early in the calendar was 1913. And before that, in 1856.

If you are 50 years old, the earliest Easter in your lifetime came on March 26 (in 1967, 1978 and 1989). In 1951, Easter fell on March 25; in 1940, March 24.

Easter in 2038 will be observed as late as it can possibly come, on April 25!

Easter comes at a time of the year where the weather is transforming from winter to spring. Christmas is celebrated as cold and sometimes snowy and the Fourth of July is probably sunny and hot. Easter can be celebrated during both of these extremes.

For example, in 1970 Easter fell on March 29, where a snowstorm hit the northeast, canceling a famous Easter parade in New York City. Yet six years later, when Easter fell on April 18, the hottest Easter was recorded.

Palm Sunday is the Sunday before Easter. This year is an oddity, because it fell on the day before St. Patrick's Day, which is a very rare occurrence.