After all, days and years have to be natural units in any calendar system.

A calendar system is a way for historians to decipher the time of an event.

Most calendar systems have twelve months in a year.

But over all the errors cancel each other, and the calendar system remains accurate.

Among the various calendar systems in use, two were particularly central and widespread across Mesoamerica.

IN.gov is currently in the process of moving agency events and press releases to a new calendar system!

A full calendar system has a different calendar date for every day.

He became a well-known scholar specializing in the field of calendar systems.

Create a good calendar system, with a daily to-do list.

However, similar issues have been raised as to other calendar systems and they're no less valid for that.