Gregorian calendar
Common years always begin and end on the same day of the week, since 364 (365 - 1) is a multiple of 7, the number of days in a week. For example, 2003 began on a Wednesday and ended on a Wednesday. Leap years end on the next day of the week from which they begin. For example, 2004 began on a Thursday and ended on a Friday.
Not counting leap years, any calendar date will move to the next day of the week the following year. For example, if your birthday fell on a Tuesday in 2002, it fell on a Wednesday in 2003. Leap years make things a little more complicated. 2004 was a leap year, so calendar days of March 1 or later in the year, moved two days of the week from 2003. However, calendar days occurring before March 1 do not make the extra day of the week jump until the year following a leap year. So, if your birthday is June 15, then it must have fallen on a Sunday in 2003 and a Tuesday in 2004. If, however, your birthday is February 15, then it must have fallen on a Saturday in 2003, a Sunday in 2004 and a Tuesday in 2005.
In any year (even a leap year), July always begins on the same day of the week that April does. Therefore, the only difference between a July calendar page and an April calendar page in the same year is the extra day July has. The same relationship exists between September and December as well as between March and November. Add an extra day to the September page and you've got December. Take a day away from the March page and you've got November. In common years only, there are additional matches: October duplicates January, and March and November duplicate February in their first 28 days. In leap years only, there is a different set of additional matches: July is a duplicate of January while February is duplicated in the first 29 days of August.
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See also
- World Calendar
- Calculation of Julian day
- Calendar reform
- Computus for a more complete description of the lunar aspects of the Gregorian calendar
- Greek Old Calendarists
- List of calendars
- Dual dating
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References
- Blackburn, B. & Holford-Strevens, L. (1999). The Oxford Companion to the Year. Oxford University Press ISBN 0-19-214231-3. Pages 98-99.
- Coyne, G. V., Hoskin, M. A., and Pedersen, O.(Eds.) (1983). Gregorian reform of the calendar: Proceedings of the Vatican conference to commemorate its 400th anniversary, 1582-1982. Vatican City: Pontifical Academy of Sciences, Specolo Vaticano
- Duncan, D. E. (1999). Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year. Harper Perennial. ISBN 0-380-79324-5.
- Gregory XIII. (2002). Inter Gravissimas (W. Spenser & R. T. Crowley, Trans.). International Organization for Standardization. (Original work published 1582)
- Online Etymology Dictionary retrieved August 23, 2006
- Seidelmann, P. K. (Ed.). (1992). Explanatory Supplement to the Astronomical Almanac. Sausalito, CA: University Science Books.
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Footnotes
- ^ This era was created in the 6th century by Roman monk Dionysius Exiguus
- ^ "Common Era". Merriam Webster Online Dictionary. (2003). Merriam-Webster. Retrieved on 2007-12-13. “Main Entry: Common Era – Function: noun – Date: 1846 – : christian era”
- ^ Introduction to Calendars. (13 September 2007). United States Naval Observatory.
- ^ "Lastly, in consideration of the quarter of a day, which he regarded as completing the true year, he established the rule that, at the end of every four years, a single day should be intercalated where the month had been hitherto inserted, that is, immediately after the terminalia; which day is now called the bissextum". Censorinus:The Natal Day.
- ^ "Julius Caesar added ten days to the former number in order to complete the 365 days which the sun takes to pass through the zodiac; and to take account of the quarter of a day, he directed the pontiffs, who were entrusted with the months and days, to intercalate one day every four years in the same month and in the same place the ancients had intercalated, that is, before the last five days of February, hence this day was called bissextile." Macrobius: Saturnalia.
- ^ Coyne et al. (Eds), (1993), pp. 201–224.
- ^ O. Pedersen. (1983). "The ecclesiastical calendar and the life of the church." in G. V. Coyne et al., ed. 42–43.
- ^ This is 365;14,33 days in sexagesimal notation—the length of the tropical year, rounded to two sexagesimal positions; this was the value used in the major astronomical tables of the day.
- ^ Coyne et. al (Eds), 1983, p. 211, 214.
- ^ Toke Nørby. The Perpetual Calendar: What about France?
- ^ Morgan, Hiram (2006-04-01). ‘The Pope’s new invention’: the introduction of the Gregorian calendar in Ireland, 1583-1782 (MS Word). ‘Ireland, Rome and the Holy See: History, Culture and Contact’, a UCC History Department symposium. Retrieved on 2007-10-17.
- ^ Nørby, Toke. The Perpetual Calendar
- ^ a b c d Mike Spathaky Old Style and New Style Dates and the change to the Gregorian Calendar: A summary for genealogists
- ^ The Korea Times: [The Dawn of Modern Korea] (266) Lunar Calendar
- ^ Tuesday 31 December 1661, Pepys Diary "I sat down to end my journell for this year, ..."
- ^ a b Nørby, Toke. The Perpetual Calendar: What about England Version 29 February 2000
- ^ House of Commons Journal Volume 8, 9 June 1660 (Regicides). British History Online. Retrieved on 2007-03-18.
- ^ a b Death warrant of Charles I web page of the UK National Archives. A demonstration of New Style meaning Julian calendar with a start of year adjustment.
- ^ The Change of New Year's Day
- ^ Denmark named 1 January as the New Year in the early 14th century according to R.W. Bauer (Calender for Aarene fra 601 til 2200, 1868/1993 ISBN 87-7423-083-2) although the number of the year did not begin on January 1 until 1559.
- ^ Benjamin Woolley, The Queen's Conjurer: The science and magic of Dr. John Dee, adviser to Queen Elizabeth I (New York: Henry Holt, 2001) p.173
- ^ In Scotland the legal start of year had been moved to 1 January in 1600 (Mike Spathaky. Old Style New Style dates and the change to the Gregorian calendar); and as Ireland was not part of the union of Great Britain so separate legislation was needed for Ireland.
- ^ The October (November) Revolution Britannica encyclopaedia, A demonstration of New Style meaning the Gregorian calendar.
- ^ Stockton, J.R. Date Miscellany I: The Old and New Styles "The terms 'Old Style' and 'New Style' are now commonly used for both the 'Start of Year' and 'Leap Year' [(Gregorian calendar)] changes (England & Wales: both in 1752; Scotland: 1600, 1752). I believe that, properly and historically, the 'Styles' really refer only to the 'Start of Year' change (from March 25th to January 1st); and that the 'Leap Year' change should be described as the change from Julian to Gregorian."
- ^ Adriana Rosado-Bonewitz, "Whats in a word?" (pdf, 1.3MB), Intercambios: Quarterly Newsletter of the Spanish Language Division of the American Translators, 9(1) (March 2005) 14-15, ISSN 1550-2945 (in Spanish)
- ^ Anatoly Liberman, "On A Self-Congratulatory Note, Or, All The Year Round: The Names of The Months" (filed in Oxford Etymologist, March 7, 2007)
- ^ L.L. Neuru, "St. Valentine's Holiday" Labyrinth 64 (1996), Department of Classical Studies, University of Waterloo, Ontario, Canada
- ^ Seidelmann, 1992, pp. 580–581.
- ^ Seidelman, 1992, p. 576, 698.
- ^ John Herschel, Outlines of Astronomy, 1849, p. 629.
- ^ Borkowski, K.M., (1991) "The tropical calendar and solar year", J. Royal Astronomical Soc. of Canada 85(3) 121-130, pp. 121-130.
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External links
- Calendar Converter
- Inter Gravissimas (Latin and French plus English)
- Frequently Asked Questions about Calendars
- The Perpetual Calendar Gregorian Calendar adoption dates for many countries.
- Synoptical Julian - Gregorian calendar Compare Old and New Style dates 1582–2100.
- Gregorian Calendar Printer
- Gregorian Calendar in Norwegian, with some Norwegian information
- History of Gregorian Calendar
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