noun

• Often with initial capital: the first day of a month.
• (by extension) A day for settling debts and other accounts.
  "To expedite theſe knots were worthy a learned and memorable Synod; while our enemies expect to ſee the expectation of the Church tir'd out with dependencies and independencies how they will compound, and in what Calends."
• (by extension, biblical, Judaism, obsolete) Synonym of Rosh Hodesh (“the Jewish festival of the new moon, which begins the months of the Hebrew calendar”).
  "The feasts of the Israelites were the Sabbath; the first day of each month, called in our translations calends, or new-moon; the three great feasts of the passover, pentecost, and tabernacles, instituted in memory of the three greatest blessings they received from God, […]"
• (rare) Synonym of calendar; (figurative) an account, a record.
  "[N]ow doth [John] Oldcastle shine: / Him for a Saint within your Kalends hold."

noun

• (obsolete, rare) plural of calend