Friday, April 22, 2011

The Easter Calendar


First I would like to say that my thoughts and prayers are with all of the people and families who have suffered because of the Texas Wildfires. I recently did a post on Possum Kingdom and am terribly saddened to know that so much of that area, and the poor animals living in the wild, has been destroyed by these fires. Please take a moment to pause and pray for everyone and everyhting involved in this devastating situation.

Happy Birthday to Me!
My birthday falls on Easter Sunday this year. While conversing with a coworker, I realized I couldn’t remember my birthday ever falling on Easter Sunday before. So of course I went to the internet to see if my birthday had indeed previously fallen on Easter or not. Check out this great link I found to the Astronomical Society of South Australia and a list of all of the dates for Easter for the years 1700 through 2299, along with loads of other useful and interesting info.

My birthday, April 24th, appears this year and not again until 2095, 84 years in between the times since my birth year (year date held hostage by it's owner pleading the 5th) my birthday falls on Easter Sunday. Then again in 2163, which is 68 years later and then 2231 which again is 68 years later. So I was right, I’ve never celebrated my birthday on Easter, not in this lifetime anyway - perhaps in another?

I vaguely recall hearing about the complicated dating method of the Easter Calendar in the past, but the information has obviously not remained in my brain and I’ve never associated the date with my own birthday before now. And the timing has definitely made me stop and think about many things. 

I have to say I feel highly special to be celebrating my birthday on such a glorious day!

This link to the *Calendars Through The Ages website has loads of information and variety of interesting calendars for various religions and nationalities. Below I am quoting from their website an explanation of what Easter is and how Easter Sunday is dated. Please visit their website for so much more interesting information.  * {Douma, Michael, curator. "The Christian Calendar-Easter" Calendars through the Ages. 2008. Institute for Dynamic Educational Development. 21, April, 2011.}

What is Easter?
In the Christian world, Easter (and the days immediately preceding it) is the celebration of the death and resurrection of Jesus in (approximately) C.E. 30.

When is Easter? (Short answer)Easter Sunday is the first Sunday after the first full moon after vernal equinox.

When is Easter? (Long answer)The calculation of Easter is complicated because it is linked to (an inaccurate version of) the Hebrew calendar. Jesus was crucified immediately before the Jewish Passover, which is a celebration of the Exodus from Egypt under Moses. Celebration of Passover started on the 15th day of the (spring) month of Nisan. Jewish months start when the moon is new, therefore the 15th day of the month must be immediately after a full moon. It was therefore decided to make Easter Sunday the first Sunday after the first full moon after vernal equinox. Or more precisely: Easter Sunday is the first Sunday after the "official" full moon on or after the "official" vernal equinox. The official vernal equinox is always 21 March. The official full moon may differ from the real full moon by one or two days. (Note, however, that historically, some countries have used the real (astronomical) full moon instead of the official one when calculating Easter. This was the case, for example, of the German Protestant states, which used the astronomical full moon in the years 1700-1776. A similar practice was used in Sweden in the years 1740-1844 and in Denmark in the 1700s.) The full moon that precedes Easter is called the Paschal full moon.

Two concepts play an important role when calculating the Paschal full moon: The Golden Number and the Epact. They are described in the following sections. The following sections give details about how to calculate the date for Easter. Note, however, that while the Julian calendar was in use, it was customary to use tables rather than calculations to determine Easter. The following sections do mention how to calculate Easter under the Julian calendar, but the reader should be aware that this is an attempt to express in formulas what was originally expressed in tables. The formulas can be taken as a good indication of when Easter was celebrated in the Western Church from approximately the 6th century.

What is the Golden Number?
Each year is associated with a Golden Number. Considering that the relationship between the moon’s phases and the days of the year repeats itself every 19 years (see astronomical basis for calendars), it is natural to associate a number between 1 and 19 with each year. This number is the so-called Golden Number. It is calculated thus:
Golden Number = (year mod 19)+1

In years which have the same Golden Number, the new moon will fall on (approximately) the same date. The Golden Number is sufficient to calculate the Paschal full moon in the Julian calendar.

How does one calculate Easter then?
Under the Julian calendar the method was simple. If you know the Golden Number of the year, you can find the Paschal full moon in this table: (Please see website for the table)

Can't have an Easter without
Easter eggs and bunnies!

Happy Birthday to all the April birthdayers

 and especially to the April 24th, Easter Sunday, celebraters!

Wendy Treitel


  1. Very informative Wendy. Great Post! And Happy Birthday, Bunny Girl!:)


  2. Wendy, Happy Birthday on Sunday. My dad's birthday sometimes fell on Easter. I always made him a coconut cake for his birthday, so I think of coconut cake as an Easter food. LOL