The planetarium show will explore the astronomical events associated
with the first day of spring and will demonstrate how the position
of the equinox has changed over the millennia with respect to the
fixed stars. The vernal equinox which is both a time and a direction
in space is called the first point of Aries. Come find out how the
Vernal Equinox got to be in Pisces now and when last it was in
Aries. Help us celebrate Noruz the oldest
continuously celebrated human holiday. The Vernal equinox was in
Taurus when this celebration began 5,000 year ago. Find out when we
will really enter the age of Aquarius, when the Vernal Equinox is in
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 =
Sidereal year: 365 days 6 hours 9 minutes 10 seconds = 365.25640
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,
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
9.2 seconds of arc/18.6 years of the obliquity of the ecliptic.