Fulvius Nobilior
Marcus Fulvius Nobilior, consul in 189 BCE, who published a calendar and set up his fasti in the temple of Hercules of the Muses.
How the Romans fixed the year
Censorinus, On the Birthday 20–22 (238 CE), in the edition of Friedrich Hultsch (Leipzig, 1867) · 238 CE
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.
Nomina decem mensibus antiquis Romulum fecisse Fulvius et Iunius auctores sunt. et quidem duos primos a parentibus suis nominasse, Martium a Marte patre, Aprilem ab Aphrodite, id est Venere, unde maiores eius oriundi dicebantur. proximos duos a populo, Maium a maioribus natu, Iunium a iunioribus. ceteros ab ordine quo singuli erant, Quintilem usque Decembrem perinde a numero.
Fulvius and Junius report that Romulus named the ten ancient months. He named the first two after his parents: March (Martius) after his father, Mars, and April (Aprilis) after Aphrodite, that is, Venus, from whom his ancestors were said to descend. He named the next two after the people: May (Maius) after the elders (maiores), and June (Iunius) after the younger men (iuniores). The rest, from Quintilis to December, he named by their place in order, by number.
Where the months got their names
Macrobius, Saturnalia 1.12–14 (early fifth century CE), in the edition of Franz Eyssenhardt (Leipzig, 1893) · early fifth century CE; the dialogue is set in the 380s
Maium Romulus tertium posuit. de cuius nomine inter auctores lata dissensio est. nam Fulvius Nobilior in fastis, quos in aede Herculis Musarum posuit, Romulum dicit, postquam populum in maiores iunioresque diuisit, ut altera pars consilio, altera armis rem publicam tueretur, in honorem utriusque partis hunc Maium, sequentem Iunium mensem uocasse.
Romulus put May third. Writers disagree widely about its name. Fulvius Nobilior wrote about it in the calendar he set up in the temple of Hercules of the Muses. He says that Romulus divided the people into the elders (maiores) and the younger men (iuniores). One group was to guard the state with counsel and the other with arms. In honor of each group Romulus called this month Maius and the next Iunius.