The Collaborative International Dictionary
Roman calendar \Roman calendar\ The calendar of the ancient Romans, from which our modern calendars are derived. It is said to have consisted originally of ten months, Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December, having a total of 304 days. Numa added two months, Januarius at the beginning of the year, and Februarius at the end, making in all 355 days. He also ordered an intercalary month, Mercedinus, to be inserted every second year. Later the order of the months was changed so that January should come before February. Through abuse of power by the pontiffs to whose care it was committed, this calendar fell into confusion. It was replaced by the Julian calendar. In designating the days of the month, the Romans reckoned backward from three fixed points, the calends, the nones, and the ides. The calends were always the first day of the month. The ides fell on the 15th in March, May, July (Quintilis), and October, and on the 13th in other months. The nones came on the eighth day (the ninth, counting the ides) before the ides. Thus, Jan. 13 was called the ides of January, Jan. 12, the day before the ides, and Jan. 11, the third day before the ides (since the ides count as one), while Jan. 14 was the 19th day before the calends of February.
Wikipedia
The Roman calendar changed its form several times between the founding of Rome and the fall of the Roman Empire. The common calendar widely used today is known as the Gregorian calendar and is a refinement of the Julian calendar where the average length of the year has been adjusted from 365.25 days to 365.2425 days (a 0.002% change).
From at least the period of Augustus on, calendars were often inscribed in stone and displayed publicly. Such calendars are called fasti.
Usage examples of "roman calendar".
Admittedly, the Roman calendar does not mesh perfectly with astrological markers, so there is some gray area in the prediction.
That name, with the addition of saint, is inserted in the Roman calendar.
Appropriately, the first month of the Roman calendar was named in his honor: January.
The Lupercalia were celebrated on the fifteenth of February and were among the most important festivals on the Roman calendar.
This was, indeed, a bad failure, for this animal would now be dubbed a martyr, and would take his place among the saints of the Roman calendar.