Alba Longa
The chief city of the Latins in the Alban Hills southeast of Rome; in legend Romulus was born of its kings. Its calendar gave March 36 days.
Today: Alban Hills, Lazio, Italy
How the Romans fixed the year
Censorinus, On the Birthday 20–22 (238 CE), in the edition of Friedrich Hultsch (Leipzig, 1867) · 238 CE
Sed ut hos annos omittam caligine iam profundae vetustatis obductos, in his quoque, qui sunt recentioris memoriae et ad cursum lunae vel solis instituti, quanta sit varietas facile est cognoscere, si quis vel in unius Italiae gentibus, ne dicam peregrinis, velit inquirere. nam ut alium Ferentini alium Lavinii itemque Albani vel Romani habuerunt annum, ita et aliae gentes. omnibus tamen fuit propositum suos civiles annos varie intercalandis mensibus ad unum illum verum naturalemque corrigere.
But let me pass over these years [of the earliest peoples], already lost in the darkness of the distant past. Even among the years of more recent memory, set by the course of the moon or the sun, it is easy to see how much variety there is. One only has to look at the peoples of Italy alone, to say nothing of foreign ones. The people of Ferentinum had one year, those of Lavinium another, the Albans and the Romans others again, and so did other peoples. But all of them aimed to correct their civil years to match the one true, natural year, by inserting extra months in different ways.
de quibus omnibus disserere quoniam longum est, ad Romanorum annum transibimus. Annum vertentem Romae Licinius quidem Macer et postea Fenestella statim ab initio duodecim mensum fuisse scripserunt: sed magis Iunio Gracchano et Fulvio et Varroni et Suetonio aliisque credendum, qui decem mensum putarunt fuisse, ut tunc Albanis erat, unde orti Romani.
It would take too long to discuss all of these, so I will move on to the year of the Romans. Licinius Macer, and later Fenestella, wrote that the year at Rome had twelve months from the very beginning. But we should rather believe Junius Gracchanus, Fulvius, Varro, Suetonius and others, who thought it had ten months. So it was at that time among the Albans, from whom the Romans came.
apud Albanos Martius est sex et triginta, Maius viginti duum, Sextilis duodeviginti, September sedecim: Tusculanorum Quintilis dies habet XXXVI, October XXXII, idem October apud Aricinos XXXVIIII.
Among the Albans, March has 36 days, May 22, Sextilis 18 and September 16. At Tusculum, Quintilis has 36 days and October 32, and at Aricia October has 39.