Changes

A '''calendar''' is any system that uses observations of cyclic motions of celestial bodies and/or the [[climate]] seasons on [[Earth]] to schedule or record the activities of human beings, or one that uses mathematics to approximate such observations.<ref name=Walker>Walker, John. "[http://www.fourmilab.ch/documents/calendar/ Fourmilab Calendar Converter]." Fourmilab Switzerland. Accessed April 9, 2008.</ref><ref name=France>"[http://www.imcce.fr/page.php?nav=fr/ephemerides/astronomie/Promenade/pages2/277.html Chronologie, eres, et calendriers]" (Chronology, Eras, and Calendars). [http://www.imcce.fr/imcce_en.html Institut de mécanique célèste et de calcul des éphémerides] (Institute of Celestial Mechanics and Ephemeral Calculation), Paris, [[France]]. Accessed April 9, 2008.</ref>

A '''calendar''' is any system that uses observations of cyclic motions of celestial bodies and/or the [[climate]] seasons on [[Earth]] to schedule or record the activities of human beings, or one that uses mathematics to approximate such observations.<ref name=Walker>Walker, John. "[http://www.fourmilab.ch/documents/calendar/ Fourmilab Calendar Converter]." Fourmilab Switzerland. Accessed April 9, 2008.</ref><ref name=France>"[http://www.imcce.fr/page.php?nav=fr/ephemerides/astronomie/Promenade/pages2/277.html Chronologie, eres, et calendriers]" (Chronology, Eras, and Calendars). [http://www.imcce.fr/imcce_en.html Institut de mécanique célèste et de calcul des éphémerides] (Institute of Celestial Mechanics and Ephemeral Calculation), Paris, [[France]]. Accessed April 9, 2008.</ref>

*Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals.<ref> [http://www.infoplease.com/spot/gregorian1.html Information Please]</ref>

*Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals.<ref>[http://www.infoplease.com/spot/gregorian1.html Information Please]</ref>

== History ==

== History ==

''Solar calendars'' synchronize strictly to the apparent motions of the [[sun]]. Phases of the moon tend to occur almost at random within any given month, but solar calendars tend to track faithfully with agricultural seasons over many years. The [[Julian Calendar]] and its successor the [[Gregorian Calendar]] are the two solar calendars in most widespread use today.

''Solar calendars'' synchronize strictly to the apparent motions of the [[sun]]. Phases of the moon tend to occur almost at random within any given month, but solar calendars tend to track faithfully with agricultural seasons over many years. The [[Julian Calendar]] and its successor the [[Gregorian Calendar]] are the two solar calendars in most widespread use today.

''Luni-solar calendars'' begin and end their months by the phases of the moon, but adjust themselves to track the sun as well. The modern [[Hebrew Calendar]] is the best-known luni-solar calendar in use today. The [[Biblical Calendar]] was supposed, by [[Sir Isaac Newton]], to be a luni-solar calendar<ref name=newton/>. But in fact it was probably a ''luni-seasonal'' calendar that relied on the ripening of a particular crop to signal the first month of [[spring]].<ref name=Jones>[[Floyd Nolen Jones|Jones, Floyd N.]] ''[[The Chronology of the Old Testament]]'', 16th ed. Green Forest, AR: Master Books, 1993-2007 (ISBN 9780890514160), pp. 106-109</ref>

''Luni-solar calendars'' begin and end their months by the phases of the moon, but adjust themselves to track the sun as well. The modern [[Hebrew Calendar]] is the best-known luni-solar calendar in use today. The [[Biblical Calendar]] was supposed, by [[Sir Isaac Newton]], to be a luni-solar calendar.<ref name=newton/> But in fact it was probably a ''luni-seasonal'' calendar that relied on the ripening of a particular crop to signal the first month of [[spring]].<ref name=Jones>[[Floyd Nolen Jones|Jones, Floyd N.]] ''[[The Chronology of the Old Testament]]'', 16th ed. Green Forest, AR: Master Books, 1993-2007 (ISBN 9780890514160), pp. 106-109</ref>

=== Agricultural calendars ===

=== Agricultural calendars ===

{{reflist|2}}

{{reflist|2}}

== See Also ==

== See also ==

* [[Gregorian Calendar]]

* [[Gregorian Calendar]]

* [[Julian Calendar]]

* [[Julian Calendar]]