The division of the year into months, weeks, and days and the method of ordering the years (past, present, and future): Virginia checked the calendar in her kitchen to see what day of the week her daughter's birthday was on in June.

From year one, an assumed date of the birth of Jesus, dates are calculated backwards (B.C., "before Christ" or B.C.E., "before common era") and forwards (A.D., Latin anno Domini, "in the year of the Lord", or C.E. "common era").

A measure of the year based on twelve lunar months: The lunar calendar is formed by employing the time it takes the Moon to revolve around the Earth), which lasts about 354.37 days.

A measure of the year based on Earth's revolution around the Sun, which takes 365.2422 days: The solar calendar is used in most countries of the world today.