- the first day of a month.
- February contained only 28 days: it had four nones like January and eight ides like all the other months; its ides were upon the 13th day of the month; and consequently after the ides there would remain only 15 days in the month: the first of these, by an inclusive reckoning, was called the 16th of (or before) the calends of March. – T. Rutherford, A System of Natural Philosophy
- the first day of a season.
- Whoever shall sell sheep, let him be answerable for three diseases (scab and rot and red water) until they receive their fill three times of the new grass in spring, if after the calends of winter he sells them. — Arthur Wade-Evans, Welsh Medieval Law
the first day of the Roman month