The duration of the true solar day

[ricci]

The interval of the time between two consecutive transits of the center of the Sun trough the meridian of a given place is called a true solar day. This interval is not constant but varies between 23h59m39s and 24h0m30s, with the present values of the obliquity of the ecliptic...

http://www.pierpaoloricci.it/dati/gi...revero_eng.htm

[mswhin63 (Malcolm)]

Is this the effect of the planetary wobble of Earth, or something else different again.