Easter Cookies and Calendars
What could this topic possibly have to do with astronomy? Well... I'm a "Cookie Monster" at heart, and since my wife is not a dessert person (except for anything chocolate), I have always been the anointed cookie maker in our house. There are cookie cutters for just about all the holidays. Until my daughters grew up and moved away, they always helped with the cookie-making, and one of the things they learned was that we always used the cookie cutter shaped like a crescent moon at Easter. Why? It is the phase of the moon that determines the date of Easter. As you know, the holiday is observed on the Sunday immediately following the first full moon after the spring (vernal) equinox - April 15 this year. Since we really don't know the exact dates on which biblical events occurred, this convention for setting the date of Easter is probably as good as any.
And the calendar? The Gregorian calendar that we use today is named after Pope Gregory XIII and originated in the Roman Catholic Church's desire to correct the Julian calendar. The Julian year was eleven minutes longer than the astronomical year, and by the 16th Century the date of the vernal equinox had become displaced by ten days. In order to effect the correction, it was necessary to drop ten days to get everything in synch. The purpose of the new calendar was to more accurately set the dates for the observance of Easter, but it ended up as a very practical thing to do.
If you have a computer program that provides calendars for any dates in history, it's an interesting exercise to call up the month of September 1752. It was in that month that the British Empire (and what would eventually become the United States of America) finally adopted the Gregorian calendar, which had already been in use on the European continent since October 1592. (The delay was due to the Church of England's prejudice against anything instigated by the Church of Rome.) UNIX systems generally show September 1752 missing ten days. If a program doesn't show any missing days either in October 1592 or September 1752, then it's inaccurate from a historical standpoint.
Islamic religions often use the phase of the moon as the basis for determining religious observances. For Christians, Easter is the one movable feast dictated by an astronomical body. Anyhow, on what other holiday are you going to use a cookie cutter shaped like a crescent moon?Published in the April 2001 issue of the NightTimes