I. PRELIMINARY NOTIONS
4. A LUSTRUM
To end these preliminary notions on a more literary note, we shall study the vocabulary. In French the word lustrum - lustre - has 3 different meanings :
- a centre light fixed on the ceiling
- the radiance of a shining object, e.g : to give new lustre
- a 5 years period
This last meaning stems from the Roman tradition of expiatory sacrifices that took place every 5 years, at the end of the people census, which is undoubtedly a remain of an ancient lunar cycle of 62 lunations at the end of which the sun took back a place in the sky very similar to that it held 5 years before.
But why should we call such a duration a lustrum?
The second meaning of the word will answer to that question.
To lustre means to impart luster
in order to be noticed (hence the biographies of "illustrious" people !).
This duration of 62 lunations is the shortest time when one is able to notice that the return of a "neomenie"
9 is not alternatively of 29 and 30 days, i.e. 1 829 days, but takes place two days later, which is unequivocal.
The word "lustre" - lustrum - shows with no ambiguity, through its various meanings, that the average lunation lasting 29,53 days had been known... since many lustra.
For further details on the lustrum structure, see Annexes p 77.
