Kalends, Nones and Ides: the phases of the Moon in the Roman month
Why the Romans counted days from the Kalends, Nones and Ides: the pontiff who called the month, the full moon sacred to Jupiter and Augustus's Greek Kalends.
The Romans did not number the days of the month from one to thirty as we do. They counted backwards from three fixed days: the Kalends, the Nones and the Ides. An expression such as the third day before the Ides of March meant 13 March, because Roman counting included both the starting day and the day of arrival. Behind this system, which seems cumbersome to us, lies the memory of an ancient lunar month.
The day the month was called
The Kalends were the first day of the month and originally coincided with the new Moon. The name, according to Varro and Macrobius, comes from the archaic verb calare, to call: a junior pontiff watched the sky and, when the first crescent appeared, summoned the people to the Capitol to announce how many days remained until the Nones. From kalendae also comes our word calendar, through the Latin calendarium, the register of debts that fell due on the Kalends.
Macrobius adds that the pontiff repeated the word calo five or seven times, depending on whether the Nones fell on the fifth or the seventh day. The Kalends were sacred to Juno, invoked also as Lucina, protector of childbirth, and on that day the regina sacrorum, wife of the king of sacrifices, offered her a sacrifice in the Regia, the ancient religious seat in the Forum.
Nones and Ides, first quarter and full moon
The Nones fell on the fifth day of the month, or on the seventh in March, May, July and October. The name means ninth, because the Nones were the ninth day before the Ides by inclusive counting. Originally they must have corresponded to the first quarter of the Moon, and according to Varro on that day country people came into the city to learn from the king the festivals of the month.
The Ides fell on the thirteenth day, or on the fifteenth in the same four months, and originally marked the full moon. They were sacred to Jupiter, to whom, as ancient sources record, a sheep called the ovis idulis was offered on that day. The etymology is uncertain; the ancients already linked it to an Etruscan verb that supposedly meant to divide, because the Ides split the month in half.
From the Ides of March to the Middle Ages
The system survived Caesar's reform intact, even though the Julian month no longer had any relation to the phases of the Moon. The Ides of March of 44 BC, the day of Caesar's murder, remain the most famous Roman date. In the archaic year, which began in March, the Ides of that month were in theory the first full moon of the new year, and they coincided with the festival of Anna Perenna, a goddess linked to the renewal of the year.
Medieval chanceries, including the papal one, went on dating documents by Kalends, Nones and Ides throughout the Middle Ages and beyond. In liturgical calendars the columns of days showed, next to the Roman date, the Sunday letters and the golden numbers that marked the new moons: the Moon, having left the structure of the month, thus returned as a tool for calculating Easter.
The echo of that system can still be heard in language today. Calendar, the Ides of March, putting something off until the Greek Kalends, that is, to a day that will never come, because the Greeks had no Kalends: Suetonius attributes the last expression to Augustus, who used it of unreliable debtors. Words born to follow the Moon thus go on speaking of time more than two thousand years later.