The only known Gallic calendar dates back to the first century BC and was found in 1897 in a field near Coligny (Ain). It is on display in the Gallo-Roman Museum of Lyon (on the slopes of FourviËre Hill). The calendar is the longest inscription in the Gallic language that we know of. Engraved in a bronze plaque measuring approximately 1.5 m x 0.90 m, the calendar, although unfortunately incomplete, is recognisable from the fragments.The plaque is composed of a series of months, all called by their Gallic name, divided into five years. The basic unit of the Gallic calendar is the "nycthÈmËre", in other words a 24-hour period of one night followed by one day. This unit was known as "latis" (or the plural "lates"). The date changed at sunset and not at midnight as in the case of the Gregorian calendar. The lates had no proper name but it is almost certain that they were referred to by ordinal numerical adjectives: Cintuxos, Alios, Tritios, Petuarios, Pempatos, Suextos, Sextamos, Oxtumetos, Noumetos, Decametos, Oinodecametos, Uodecametos, Tridecametos, Petrudecametos and Pempedecametos. The lates are grouped into half months of 15 or 14 lates. One half of the waning moon (from the full moon to the new moon) and one half of the waxing moon. Since the new moon is invisible at its exact astronomical moment, the first lunar half-moon always includes 15 lates. The end of the new moon was called "Atenoux", an abbreviation of "atenouxtio" (renewal) as counting of the dates of the second half began again. Thus, the 16th of the month was dated I Atenoux and the 29th XIIII Atenoux. The lunar month lasted 29 or 30 lates to take into account the average astronomical length of the lunar month, namely 29.53058 days. Months containing an even number of lates are referred to as MAT (abbreviation of "matos", meaning complete) while uneven months are referred to as ANM (abbreviation of "anmatos", meaning defective). Months begin theoretically in the evening as the full moon rises (full moon meaning less than one day from its maximum observable astronomical moment).