Says here I'm correct and it was originally 10 months
The original Roman calendar is believed to have been a lunar calendar, which may have been based on one of the Greek lunar calendars. As the time between new moons averages 29.5 days, its months were constructed to be either hollow (29 days) or full (30 days).
KING ROMULUS -
The original Roman calendar was said to have been invented by Romulus, the first king of Rome, around 753 BCE. The calendar started the year in March (Martius) and consisted of 10 months, with 6 months of 30 days and 4 months of 31 days. The winter season was not assigned to any month, so the calendar year only lasted 304 days with 61 days unaccounted for in the winter.
Calendar of King Romulus:
Martius - 31 Days
Aprilis - 30 Days
Maius - 31 Days
Iunius - 30 Days
Quintilis - 31 Days
Sextilis - 30 Days
September - 30 Days
October - 31 Days
November - 30 Days
December - 30 Days
Romulus was legendary, so I would suspect anything attributed to him.
"Some scholars doubt the existence of this calendar at all, as it is only attested in late Republican and Imperial sources and supported only by the misplaced names of the months from September to December. Rüpke also finds the coincidence of the length of the supposed "Romulan" year with the length of the first ten months of the Julian calendar to be suspicious."
Says here I'm correct and it was originally 10 months
Martius - 31 Days Aprilis - 30 Days Maius - 31 Days Iunius - 30 Days Quintilis - 31 Days Sextilis - 30 Days September - 30 Days October - 31 Days November - 30 Days December - 30 Days
Romulus was legendary, so I would suspect anything attributed to him.
"Some scholars doubt the existence of this calendar at all, as it is only attested in late Republican and Imperial sources and supported only by the misplaced names of the months from September to December. Rüpke also finds the coincidence of the length of the supposed "Romulan" year with the length of the first ten months of the Julian calendar to be suspicious."
I win?