Thank you Piero and John.
But after your answers my problem remains.
1.
The equation of time can explain no more than about 31 minutes. The difference
I descirbe is 21 hours and 10 minutes.
2.
I describe a difference between two parts of the elliptical orbit of the earth
which are symmetrical with regard to the sun. It is not the difference between
winter and to summer but the the difference between the time from spring
equinox to midsummer on one hand and the time from midsummer to autumn equinox
on the other hand.
I look out for a further explanation.
1. The equation of time gives the difference between the sun time and
standard time. Your difference is cumulative or integral of the daily
difference. The orbital effect has a maximum difference of about 8
minutes (this does not include the inclination effect). Averaging
this approximately sinusoidal variation over 6 months is
approximately 7 minutes per day. 7 times 180 days = 21 hours.
2. As I and others have pointed out the closest approach to the sun
(perihelion) and furthest distance (aphelion) are not symmetrical
with the equinoxes which depend on the orientation of the Earth's
axis of tilt to its orbit. Previous discussions of the equation of
time in this list have indicated how these two system change with
resect to each other over very long times, changing the shape of the
equation of time.
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Cheers,
John
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