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Calendar for any common year starting on Tuesday,  




 



 




ISO 8601conformant calendar with week numbers for  




 



 




In the (currently used) Gregorian calendar, along with Thursday, the fourteen types of year (seven common, seven leap) repeat in a 400year cycle (20871 weeks). Fortyfour common years per cycle or exactly 11% start on a Tuesday. The 28year subcycle only spans across century years divisible by 400, e.g. 1600, 2000, and 2400.
Decade  1st  2nd  3rd  4th  5th  6th  7th  8th  9th  10th  

17th century  1602  1613  1619  1630  —  1641  1647  1658  1669  1675  1686  1697  
18th century  1709  1715  1726  1737  1743  1754  1765  1771  1782  1793  1799  
19th century  1805  1811  1822  1833  1839  —  1850  1861  1867  1878  1889  1895  
20th century  1901  1907  1918  1929  1935  1946  1957  1963  1974  1985  1991  
21st century  2002  2013  2019  2030  —  2041  2047  2058  2069  2075  2086  2097  
22nd century  2109  2115  2126  2137  2143  2154  2165  2171  2182  2193  2199  
23rd century  2205  2211  2222  2233  2239  —  2250  2261  2367  2278  2289  2295  
24th century  2301  2307  2318  2329  2335  2346  2357  2363  2374  2385  2391 
400 year cycle
century 1: 2, 13, 19, 30, 41, 47, 58, 69, 75, 86, 97
century 2: 109, 115, 126, 137, 143, 154, 165, 171, 182, 193, 199
century 3: 205, 211, 222, 233, 239, 250, 261, 267, 278, 289, 295
century 4: 301, 307, 318, 329, 335, 346, 357, 363, 374, 385, 391
In the nowobsolete Julian calendar, the fourteen types of year (seven common, seven leap) repeat in a 28year cycle (1461 weeks). A leap year has two adjoining dominical letters (one for January and February and the other for March to December in the Church of England as 29 February has no letter). Each of the seven twoletter sequences occurs once within a cycle, and every common letter thrice.
As the Julian calendar repeats after 28 years that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula ((year + 8) mod 28) + 1). Years 7, 18 and 24 of the cycle are common years beginning on Tuesday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Tuesday.
Decade  1st  2nd  3rd  4th  5th  6th  7th  8th  9th  10th  

15th century  1409  1415  1426  1437  1443  1454  1465  1471  1482  1493  1499  
16th century  1510  —  1521  1527  1538  1549  1555  1566  1577  1583  1594  
17th century  1605  1611  1622  1633  1639  1650  —  1661  1667  1678  1689  1695  
18th century  1706  1717  1723  1734  1745  1751  1762  1773  1779  1790  —  
19th century  1801  1807  1818  1829  1835  1846  1857  1863  1874  1885  1891  
20th century  1902  1913  1919  1930  —  1941  1947  1958  1969  1975  1986  1997  
21st century  2003  2014  2025  2031  2042  2053  2059  2070  —  2081  2087  2098 
A common year starting on Sunday is any nonleap year that begins on Sunday, 1 January, and ends on Sunday, 31 December. Its dominical letter hence is A. The most recent year of such kind was 2017 and the next one will be 2023 in the Gregorian calendar, or, likewise, 2007, 2018 and 2029 in the obsolete Julian calendar, see below for more.
A common year starting on Friday is any nonleap year that begins on Friday, 1 January, and ends on Friday, 31 December. Its dominical letter hence is C. The current year, 2021, is a common year starting on Friday in the Gregorian calendar. The last such year was 2010 and the next such year will be 2027 in the Gregorian calendar, or, likewise, 2005, 2011 and 2022 in the obsolete Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on, and occurs in century years that yield a remainder of 100 when divided by 400. The most recent such year was 1700 and the next one will be 2100.
A common year starting on Monday is any nonleap year that begins on Monday, 1 January, and ends on Monday, 31 December. Its dominical letter hence is G. The most recent year of such kind was 2018 and the next one will be 2029 in the Gregorian calendar, or likewise, 2013, 2019 and 2030 in the Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on and occurs in century years that yield a remainder of 300 when divided by 400. The most recent such year was 1900 and the next one will be 2300.
Dominical letters or Sunday letters are a method used to determine the day of the week for particular dates. When using this method, each year is assigned a letter depending on which day of the week the year starts.
A leap year starting on Sunday is any year with 366 days that begins on Sunday, 1 January, and ends on Monday, 31 December. Its dominical letters hence are AG. The most recent year of such kind was 2012 and the next one will be 2040 in the Gregorian calendar or, likewise, 1996 and 2024 in the obsolete Julian calendar.
A leap year starting on Monday is any year with 366 days that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF. The most recent year of such kind was 1996 and the next one will be 2024 in the Gregorian calendar or, likewise, 2008, and 2036 in the obsolete Julian calendar.
A common year starting on Wednesday is any nonleap year that begins on Wednesday, 1 January, and ends on Wednesday, 31 December. Its dominical letter hence is E. The most recent year of such kind was 2014, and the next one will be 2025 in the Gregorian calendar or, likewise, 2009, 2015 and 2026 in the obsolete Julian calendar, see below for more. This common year is one of the three possible common years in which a century year can begin on, and occurs in century years that yield a remainder of 200 when divided by 400. The most recent such year was 1800 and the next one will be 2200.
A leap year starting on Tuesday is any year with 366 days that begins on Tuesday, 1 January, and ends on Wednesday, 31 December. Its dominical letters hence are FE. The most recent year of such kind was 2008 and the next one will be 2036 in the Gregorian calendar or, likewise 2020 and 2048 in the obsolete Julian calendar.
A common year starting on Saturday is any nonleap year that begins on Saturday, 1 January, and ends on Saturday, 31 December. Its dominical letter hence is B. The most recent year of such kind was 2011 and the next one will be 2022 in the Gregorian calendar or, likewise, 2006, 2017 and 2023 in the obsolete Julian calendar. See below for more.
A common year starting on Thursday is any nonleap year that begins on Thursday, 1 January, and ends on Thursday, 31 December. Its dominical letter hence is D. The most recent year of such kind was 2015 and the next one will be 2026 in the Gregorian calendar or, likewise, 2010 and 2021 in the obsolete Julian calendar, see below for more.
A leap year starting on Saturday is any year with 366 days that begins on Saturday, 1 January, and ends on Sunday, 31 December. Its dominical letters hence are BA. The most recent year of such kind was 2000 and the next one will be 2028 in the Gregorian calendar or, likewise, 2012 and 2040 in the obsolescent Julian calendar. In the Gregorian calendar, years divisible by 400 are always leap years starting on Saturday. Most recently this occurred in 2000; the next such occurrence will be 2400, see below for more.
A leap year starting on Friday is any year with 366 days that begins on Friday 1 January and ends on Saturday 31 December. Its dominical letters hence are CB. The most recent year of such kind was 2016 and the next one will be 2044 in the Gregorian calendar or, likewise, 2000 and 2028 in the obsolete Julian calendar.
A leap year starting on Thursday is any year with 366 days that begins on Thursday 1 January, and ends on Friday 31 December. Its dominical letters hence are DC. The most recent year of such kind was 2004 and the next one will be 2032 in the Gregorian calendar or, likewise, 2016 and 2044 in the obsolete Julian calendar.
A leap year starting on Wednesday is any year with 366 days that begins on Wednesday 1 January and ends on Thursday 31 December. Its dominical letters hence are ED. The most recent year of such kind was 2020 and the next one will be 2048, or likewise, 2004 and 2032 in the obsolete Julian calendar, see below for more.
The determination of the day of the week for any date may be performed with a variety of algorithms. In addition, perpetual calendars require no calculation by the user, and are essentially lookup tables. A typical application is to calculate the day of the week on which someone was born or a specific event occurred.
The Doomsday rule is an algorithm of determination of the day of the week for a given date. It provides a perpetual calendar because the Gregorian calendar moves in cycles of 400 years. The algorithm for mental calculation was devised by John Conway in 1973, drawing inspiration from Lewis Carroll's perpetual calendar algorithm. It takes advantage of each year having a certain day of the week upon which certain easytoremember dates, called the doomsdays, fall; for example, the last day of February, 4/4, 6/6, 8/8, 10/10, and 12/12 all occur on the same day of the week in any year. Applying the Doomsday algorithm involves three steps: Determination of the anchor day for the century, calculation of the anchor day for the year from the one for the century, and selection of the closest date out of those that always fall on the doomsday, e.g., 4/4 and 6/6, and count of the number of days between that date and the date in question to arrive at the day of the week. The technique applies to both the Gregorian calendar and the Julian calendar, although their doomsdays are usually different days of the week.
The solar cycle is a 28year cycle of the Julian calendar, and 400year cycle of the Gregorian calendar with respect to the week. It occurs because leap years occur every 4 years and there are 7 possible days to start a leap year, making a 28year sequence.
The ISO week date system is effectively a leap week calendar system that is part of the ISO 8601 date and time standard issued by the International Organization for Standardization (ISO) since 1988 and, before that, it was defined in ISO (R) 2015 since 1971. It is used (mainly) in government and business for fiscal years, as well as in timekeeping. This was previously known as "Industrial date coding". The system specifies a week year atop the Gregorian calendar by defining a notation for ordinal weeks of the year.
The Zimmer tower is a tower in Lier, Belgium, also known as the Cornelius tower, that was originally a keep of Lier's 14thcentury city fortifications. In 1930, astronomer and clockmaker Louis Zimmer (1888–1970) built the Jubilee Clock, which is displayed on the front of the tower, and consists of 12 clocks encircling a central one with 57 dials. These clocks showed time on all continents, phases of the moons, times of tides and many other periodic phenomena.
A century leap year is a leap year in the Gregorian calendar that is evenly divisible by 400.