All that is certainly known about the antiquity of the sieu is that they were well established in the 3rd century B.C. Their initial point at the autumnal equinox marked by Kio (Spica Virginis) suits a still later date; and there is no valid evidence that the modern series resulted from the rectification of an older superannuated arrangement, analogous to the Krittika sequence of nakshatras.
In The Calendar, For Example, Which Was Attempted To Be Introduced In France In 1 793, The Beginning Of The Year Was Fixed At Midnight Preceding The Day In Which The True Autumnal Equinox Falls.
The new arrangement was regarded as beginning on the 22nd of September 1792, this day being chosen because on it the republic was proclaimed and because it was in this year the day of the autumnal equinox.
Near the autumnal equinox this angle is at a minimum; hence the phenomenon of the " harvest moon," when for several successive days the difference of times of rising on one day and the next may be only from 15 to 20 minutes.
September 21 was the " official " date of the autumnal equinox.
