from the series of short articles about calendars
Roman months just before the Julius Caesar reform had the following names and durations: Ianuarius (29), Februarius (28), Martius (31), Aprilis (29), Maius (31), Iunius (29), Quintilis (31), Sextilis (29), September (29), October (31), November (29), December (29). Sum of days: 355.
Due to the fact of the short duration of the year, Romans, as Hebrews and Greeks, intercalated in certain years one 27-day month after the 24th of February. In these cases the extra days were 27-4 =23, since the 25th until 28th of February were not included; thus the length of these specific years was 355+23= 378 days.
When Caesar returned home from Egypt and his other wars in 46 BC, he found that the many years of misuse had left the calendar in shambles, since the priests decided not to insert intercalary months, for financial and political reasons.
Caesar himself was in part to blame , since he had held the title of chief priests – pontifex maximus – for several years, and had inserted an intercalated month only once, since 52 BC. This had held the Roman year to veer off the solar year by almost two full months. Whether this was an intentional manipulation by Caesar or his allies among the priests, or a simple oversight by a pontifex maximus distracted by civil war, is unknown. Whatever the cause, it played havoc not only with farmers and sailors but also with a population becoming more dependent than ever on trade, commerce, law and civil administration in a rapidly growing empire that desperately needed a standard system for measuring time.
To fix the calendar, says Plutarch, ‘Caesar called in the best philosophers and mathematicians of his time,’ including the Alexandrian astronomer Sosigenes, who seems to have come to Rome from Alexandria to fine-tune the reforms he and Caesar had discussed in Egypt. The core of the reform was identical to the system ordered by Ptolemy III in 218 BC – a year equaling 365 ¼ days, with the fraction being taken care of by running a cycle of three 365-day years followed by a ‘leap’ year of 366 days.
To bring the calendar back in alignment with the vernal equinox, which was supposed to occur by tradition on 25th March, Caesar also ordered two extra intercalary months added to 46 BC – consisting of 33 and 34 days inserted between November and December. Combined with an intercalary month already installed in February, the entire year of 46 BC ended up stretching an extraordinary 355+23+33+34=445 days. Caesar called it the ‘utimus annus confusionis’, ‘the last year of confusion’. Everybody else called it ‘the Year of Confusion’, referring not just to the extended year , but also tho the heavy whirlwind of change inaugurated by Caesar, who in effect was launching a vast new empire that already was profoundly reordering countless lives.
The extra days in 46 BC caused disruptions throughout the Roman world in everything from contracts to shipping schedules. The Roman historian Dio Cassius writes about a governor in Gaul who insisted that taxes be assessed for Caesar’s two extra months. Cicero in Rome complained that his old political adversary Julius was not content with ruling the earth but also strove to rule the stars. Yet most Romans were relieved to have a stable and objective calendar – one based not on the whims of priests and kings, but on science.
To round his calendar reforms, Caesar moved the first of the year from March to January, nearer to the winter solstice. He then reorganized the lengths of the months to add in the ten days required to bring the year form 355 to 265 days, as follows:
Ianuarius (31), Februarius (29/30), Martius (31), Aprilis (30), Maius (31), Iunius (30), Quintilis (31), Sextilis (30), September (31), October (30), November (31), December (30). Sum of days: 365/366.
He left the old calendar largely intact in terms of feustivals and holidays. He also retained the old system of numbering days according to calends, nones and ides (see also Info Item 20), as well as the traditional names of the months, though later the Senate changed Quintilis to Julius in his honour.
When the new day dawned in in 1 January 45 BC – the kalends of Januarius 709 AUC (Ab Urbe Condita) – Romans awoke with a new calendar that was then among the most accurate in the world. Even so it remained subject to errors and tinkering by priests and politicians. The first mistake was to come soon after Caesar’s death in 44 BC, when the college of pontiffs began counting leap years every three years instead of four. This quickly threw the calendar off again, though the error was easily corrected later by Emperor Augustus. Catching the mistake in 8 BC, he ordered the next three leap years to be skipped, restoring the calendar to its proper time by the year AD 8. Since that year this calendar has never missed a leap year, until the Gregorian reform of 1582.
From the Old Roman to the Julian Calendar