Provides an overview of the Christian, Hebrew and Islamic calendars in common use. Available in a single text file, .pdf or Web page format.

Essay on the evolution of the calendar by L.E. Doggett is from "Explanatory Supplement to the Astronomical Almanac."

Explores the long and varied history of the calendar through its various incarnations.

Gives an overview of the many calendar systems and a comparison in table form. Also offers a more in-depth explanation of each calendar.

Describes the basis for the different time periods or eras in terms of astronomy, geology, archaeology, history and geography.

Virtual encyclopedia defines the term used to identify the 10th month of the Gregorian calendar.

Discusses the length and astronomical rationale for this unit of temporal measurement.

View more than you every thought possible to know about today's date, historical and religious calendars, world holidays and special clocks.