Noruz in the Wikipedia.

Cyrus the Great in the Wikipedia

Persian Calendars in the Wikipedia

Passover in the Wikipedia

Easter controversy from the Catholic Encyclopedia.

Length of the Seasons:

Winter: 88 days 23 hours 54 minutes

Spring: 92 days 18 hours 26 minutes

Summer: 93 days 15 hours 29 minutes

Autumn: 89 days 89 days 20 hours

Three main types of years

Mean Tropical year: 365 days 5 hours 48 minutes 46 seconds = 365.24220 days

Sidereal year: 365 days 6 hours 9 minutes 10 seconds = 365.25640 days

Anomalistic year from perihelion to perihelion: 365 years 6 hours 13 minutes 53 seconds = 365.25960 days

Greater discussion of types of years in the Wikipedia.

Pope Gregory XIII calendar reform October 5, 1582 = October 15, 1582.

Current Gregorian calendar system 365.24250 days per year will have only a one day error in 3,300 years. Currently the Gregorian calendar has a leap year every 4 years except on the century boundary unless the century boundary are divisible by 400 so 1700, 1800, and 1900 are not leap years, but 1600 and 2000 are leap years.

Difference between Tropical year and Sidereal year is 20 minutes 24 seconds or approximately 20.5 minutes/year, because of precession.

Crude estimate of the precession time: 365.24220 days/20.5 minutes/year * 24 hours/1 day * 60 minutes/1 hour = 25,700 years.

Nutation 9.2 seconds of arc/18.6 years of the obliquity of the ecliptic.

Keynote presentation shown 3-20-2014 as part of the planetarium show.

PowerPoint presentation shown 3-19-2012 as part of the planetarium show.

PowerPoint presentation shown 3-20-20006 as part of the planetarium show.

Fumocy, Full Moon Cycle in the Wikipedia.

Montgomery College's Planetarium home page

Web page by Dr. Harold Alden Williams.

Last changed 2:21PM on March 11 2018.