Monday, September 21, 2009
2009 Autumnal Equinox - Geometric vs Actual
Autumnal Equinox - Sep 22 2009 5:18 PM EDT. This is the official time. However the actual date of equal hours of day and night occur around the 26th of the month at 40N latitude which is near where I live. Here is a link that discusses this. The 'short-reason' for this is due to how the atmosphere bends sunlight so that you see the sun rise a bit before the geometric sunrise and you see the sun set a bit after the geometric sunset thus daylight is extended a bit. So the geometric Equinox occurs at 5:18pm EDT on the 22nd while the actual Equinox occurs on the 26.