WIKI NOTE: A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. This is done by giving names to periods, typically days, weeks, months, and years.
Ancient documents and inscriptions, such as those from Rome and China, include early forms of calendars. The modern calendar evolved alongside others such as almanacs, which collected religious, cultural, meteorological, astronomical, and astrological information in a table format; practica, which gave astrological predictions for the year ahead; and diaries for personal and professional use.
The term calendar is taken from calendae, the term for the first day of the month in the Roman calendar, related to the verb calare "to call out", referring to the "calling" of the new moon when it was first seen. Latin calendarium meant "account book, register" (as accounts were settled and debts were collected on the calends of each month).
