03/29/2013 – Ephemeris – How we know this Sunday is Easter

Ephemeris for Good Friday, Friday, March 29th.  The sun will rise at 7:28.  It’ll be up for 12 hours and 38 minutes, setting at 8:06.   The moon, 2 days past full, will rise at 11:14 this evening.

Wednesday was the day of the Paschal full moon, the full moon after the first day of spring, which is defined by Christian churches as March 21st.  For the date of Easter the actual full moon isn’t used, but a rather complicated formula is used to find the new moon.  There’s a complicated correction to then find the date of the full moon, which 2 days ago.  This year that formula works out correctly.  It can be a day off either way.  The next Sunday then is Easter.  Orthodox churches use the Julian calendar and a different formula but they’ll celebrate Easter on May 5th.  The formula was set up to approximate the Jewish lunar calendar.  It works out close this year because Passover started at sunset last Sunday night.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.