Ovid, Fasti 1.28-44
When the founder of the city was straightening out the calendar, he decreed that there be twice five months in the year. Ah Romulus, you knew arms a bit better than you knew the stars, and perhaps took greater care to conquer your neighbors. Yet, Caesar, there is a reason which moved him and he has a way to justify his error. The time which is enough for an infant to come forth from its mother’s womb he also decided was enough for the year. Through just so many months from the funeral of her husband will the wife keep up the mournful signs in her widowed home. The care of striped Quirinus saw all these things when he was giving the years’ regulations to his uneducated people. The first month belonged to Mars, the second to Venus. She was the starting point of the race, and he was its father. The third took its name from the old, the fourth from the young, and the crowd that followed was just noted by its number. But Numa didn’t skip over Janus or the ancient shades, and he added two months to the ancient ones.
Tempora digereret cum conditor Urbis, in anno
constituit menses quinque bis esse suo.
scilicet arma magis quam sidera, Romule, noras,
curaque finitimos vincere maior erat. 30
est tamen et ratio, Caesar, quae moverit illum,
erroremque suum quo tueatur habet.
quod satis est, utero matris dum prodeat infans,
hoc anno statuit temporis esse satis;
per totidem menses a funere coniugis uxor 35
sustinet in vidua tristia signa domo.
haec igitur vidit trabeati cura Quirini,
cum rudibus populis annua iura daret.
Martis erat primus mensis, Venerisque secundus;
haec generis princeps, ipsius ille pater: 40
tertius a senibus, iuvenum de nomine quartus,
quae sequitur, numero turba notata fuit.
at Numa nec Ianum nec avitas praeterit umbras,
mensibus antiquis praeposuitque duos.