The calends (Latin: kalendae, "the called") were the first days of each month of the Roman calendar. The Romans assigned these calends to the first day of the month, signifying the start of the new moon cycle. On that day, the pontiffs would announce at the Curia Calabra the rest days for the upcoming month and the debtors had to pay off their debts that were inscribed in the kalendaria, a sort of accounts book. The date (in this calendar system) was measured forward to upcoming days such as the calends, nones or ides. Thus, while modern calendars count the number of days after the first of each month, III. Kal. Ian. would be December 30th, three days (counting inclusively) before the first of January. To find the day of the calends of the current month, one counts how many days remain in the month, and add two to that number. For example, April 22, is the 10th of the calends of May, because there are 8 days left in April, to which 2 being added, the sum is 10.
Computation of the days of the month from calends can be done using the following verses:
Principium mensis cujusque vocato kalendas:
Sex Maius nonas, October, Julius, et Mars;
Quattuor at reliqui: dabit idus quidlibet octo.
meaning that the first day is called the calends; six days later is the nones of May, October, July and March; four days later for the remaining months; and the ides is eight days after that.
This word forms the basis of the English word calendar. The Latin term is traditionally written with initial K, following the ancient custom using this letter in a few words beginning with the sequence ka.
The calends was a feature of the Latin calendar, absent from the Greek calendar. Accordingly, to postpone something ad Kalendas Graecas ("to the Greek calends") meant postponing it forever. The phrase survived over the centuries in Greek and in the Romance languages (Italian: alle calende greche; French: aux calendes grecques; Portuguese: às calendas gregas; Romanian: la Calendele Grecesti; etc.).
- This article incorporates text from a publication now in the public domain: Chambers, Ephraim, ed. (1728). "article name needed". Cyclopaedia, or an Universal Dictionary of Arts and Sciences (first ed.). James and John Knapton, et al.
- Recreations in Mathematics and Natural Philosophy. Longman, Hurst, Rees, Orme, and Brown. 1814. pp. 191–2. Retrieved 2010-08-31.
- T.P. Wiseman, "The Kalends of April," in Idem, Unwritten Rome. Exeter, University of Exeter Press, 2008.