Often with initial capital: the first day of a month / (historical, Ancient Rome) the first day of a month of the Roman calendar. / (by extension) A day for settling debts and other accounts.

(obsolete, rare) plural of calend

(archaic) calendrical; relating to a calendar

(organic chemistry) Relating to calendic acid or its derivatives

(rare) According to, relating to, or concerning the calendar.

(obsolete, rare) Synonym of calends

(idiomatic) A time that never occurs; never; when pigs fly.

(organic chemistry) 8,10,12-octadecatrienoic acid

One who operates a calender.

plural of calenderer