A more thorough explanation:

Definition: Calends (kal-uhndz) refers to the first day of the month in the ancient Roman calendar.

Example: In the Roman calendar, the Calends of March was the first day of March.

Explanation: The term "Calends" was used in the ancient Roman calendar to refer to the first day of each month. For example, the Calends of March was the first day of March. This term is similar to the modern-day "first of the month" and was used to mark the beginning of a new month.