Calends n. pl. : The first day of each month in the ancient Roman calendar.

Example:


Taxonomy
Calends, free encyclopedia, Kalendae, Kalendas, search, arum, the Roman, Romans, first day, day of the month, new moon, the rest, rest days, debtors, debts, inscribed, calendar system, three days.

Defination from the web:
Calends (Latin Kalendae "the called", gen. plural -arum), correspond to the first days of each month of the Roman calendar. ... Accordingly, to postpone something ad Kalendas Graecas (to the Greek calends) meant postponing it forever. ...