presented as common in many Englishspeaking areas"}},"i":0}}]}" id="mwHg">
Calendar for any common year starting on Saturday, A common year is a calendar year with 365 days, as distinguished from a leap year, which has 366. More generally, a common year is one without intercalation. The Gregorian calendar,, employs both common years and leap years to keep the calendar aligned with the tropical year, which does not contain an exact number of days.  




 



 




ISO 8601conformant calendar with week numbers for ISO 8601Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and timerelated data. It was issued by the International Organization for Standardization (ISO) and was first published in 1988. The purpose of this standard is to provide an unambiguous and welldefined method of representing dates and times, so as to avoid misinterpretation of numeric representations of dates and times, particularly when data are transferred between countries with different conventions for writing numeric dates and times. 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.  




 



 




If the preceding year is a common year starting on Friday, then the year begins in ISO week 52; if the preceding year is a leap year starting on Thursday, then the year begins in ISO week 53.
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 most recent year of such kind was 2010 and the next one will be 2021 in the Gregorian calendar, or, likewise, 2011 and 2022 in the obsolete Julian calendar. The century year, 2100, will also be a common year starting on Friday in the Gregorian calendar. See below for more. Any common year that starts on Wednesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this common year occurs in August. Leap years starting on Thursday share this characteristic, but also have another one in February.
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, such as the years 1880, 1920, 1948, 1976, 2004, 2032, 2060, and 2088, in the Gregorian calendar or, likewise, 1988, 2016, and 2044 in the obsolete Julian calendar. Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in February and August.
In the (currently used) Gregorian calendar, alongside with Sunday, Monday, Wednesday or Friday, the fourteen types of year (seven common, seven leap) repeat in a 400year cycle (20871 weeks). Fortythree common years per cycle or exactly 10.75% start on a Saturday. The 28year subcycle will break at a century year which is not divisible by 400 (e.g. it broke at the year 1900 but not at the year 2000).
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, 2018 and 2029 in the obsolete Julian calendar, see below for more. Any common year that starts on Sunday, Monday or Tuesday has two Friday the 13ths. This common year contains two Friday the 13ths in January and October.
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 obsolete Julian calendar. The century year, 1900, was also a common year starting on Monday in the Gregorian calendar. See below for more. Any common year that starts on Sunday, Monday or Tuesday has two Friday the 13ths. This common year of this type contains two Friday the 13ths in April and July. Leap years starting on Sunday share this characteristic, but also have another in January.
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. The century year, 1800, was also a common year starting on Wednesday in the Gregorian calendar, see below for more. Any common year that starts on Wednesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this common year occurs in June. Leap years starting on Tuesday share this characteristic.
1st  2nd  3rd  4th  5th  6th  7th  8th  9th  10th  

16th century  prior to first adoption (proleptic)  1583  1594  
17th century  1605  1611  1622  1633  1639  1650  —  1661  1667  1678  1689  1695  
18th century  1701  1707  1718  1729  1735  1746  1757  1763  1774  1785  1791  
19th century  1803  1814  1825  1831  1842  1853  1859  1870  —  1881  1887  1898  
20th century  1910  —  1921  1927  1938  1949  1955  1966  1977  1983  1994  
21st century  2005  2011  2022  2033  2039  2050  —  2061  2067  2078  2089  2095 
Year starts  Common years  Leap years  

1 Jan  Count  Ratio  31 Dec  DL  DD  Count  Ratio  31 Dec  DL  DD  Count  Ratio  
Sun  58  14.50 %  Sun  A  Tue  43  10.75 %  Mon  AG  Wed  15  3.75 %  
Sat  56  14.00 %  Sat  B  Mon  43  10.75 %  Sun  BA  Tue  13  3.25 %  
Fri  58  14.50 %  Fri  C  Sun  43  10.75 %  Sat  CB  Mon  15  3.75 %  
Thu  57  14.25 %  Thu  D  Sat  44  11.00 %  Fri  DC  Sun  13  3.25 %  
Wed  57  14.25 %  Wed  E  Fri  43  10.75 %  Thu  ED  Sat  14  3.50 %  
Tue  58  14.50 %  Tue  F  Thu  44  11.00 %  Wed  FE  Fri  14  3.50 %  
Mon  56  14.00 %  Mon  G  Wed  43  10.75 %  Tue  GF  Thu  13  3.25 %  
∑  400  100.0 %  303  75.75 %  97  24.25 % 
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.
The solar cycle is a 28year cycle of the Julian 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.
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 10, 16 and 27 of the cycle are common years beginning on Saturday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Saturday.
Decade  1st  2nd  3rd  4th  5th  6th  7th  8th  9th  10th  

15th century  1401  1407  1418  1429  1435  1446  1457  1463  1474  1485  1491  
16th century  1502  1513  1519  1530  —  1541  1547  1558  1569  1575  1586  1597  
17th century  1603  1614  1625  1631  1642  1653  1659  1670  —  1681  1687  1698  
18th century  1709  1715  1726  1737  1743  1754  1765  1771  1782  1793  1799  
19th century  1810  —  1821  1827  1838  1849  1855  1866  1877  1883  1894  
20th century  1905  1911  1922  1933  1939  1950  —  1961  1967  1978  1989  1995  
21st century  2006  2017  2023  2034  2045  2051  2062  2073  2079  2090  — 
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, such as the years 1888, 1928, 1956, 1984, 2012, 2040, 2068, 2096, 2108, 2136, 2164, and 2192 in the Gregorian calendar or, likewise, 1996 and 2024 in the obsolete Julian calendar.
A common year starting on Tuesday is any nonleap year that begins on Tuesday, 1 January, and ends on Tuesday, 31 December. Its dominical letter hence is F. The current year, 2019, is a common year starting on Tuesday in the Gregorian calendar. The last such year was 2013 and the next such year will be 2030, or, likewise, 2014 and 2025 in the obsolete Julian calendar, see below for more. Any common year that starts on Sunday, Monday or Tuesday has two Friday the 13ths. This common year contains two Friday the 13ths in September and December. Leap years starting on Monday share this characteristic. From July of the year that precedes this year until September in this type of year is the longest period that occurs without a Friday the 13th. Leap years starting on Saturday share this characteristic, from August of the common year that precedes it to October in that type of year.
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, such as the years 1720, 1748, 1776, 1816, 1844, 1872, 1912, 1940, 1968, 1996, 2024, 2052, 2080, and 2120 in the Gregorian calendar or, likewise, 2008, 2036, and 2064 in the obsolete Julian calendar. Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in September and December. Common years starting on Tuesday share this characteristic.
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, such as the years 1884, 1924, 1952, 1980, 2008, 2036, 2064, 2092, and 2104 in the Gregorian calendar or, likewise, 1964, 1992, and 2020 in the obsolete Julian calendar. Any leap year that starts on Tuesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this leap year occurs in June. Common years starting on Wednesday share this characteristic.
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. This common year contains the most Friday the 13ths; specifically, the months of February, March, and November. Leap years starting on Sunday share this characteristic. From February until March in this type of year is also the shortest period that occurs within a Friday the 13th.
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, such as the years 1820, 1848, 1876, 1916, 1944, 1972, 2000, 2028, 2056, 2084, 2124, 2152, and 2180 in the Gregorian calendar or, likewise, 2012 and 2040 in the obsolete Julian calendar. In the Gregorian calendar all centennial leap years start on Saturday; the next such year 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, such as the years 1808, 1836, 1864, 1892, 1904, 1932, 1960, 1988, 2016, 2044, 2072, 2112, 2140, 2168 and 2196 in the Gregorian calendar or, likewise, 2000 and 2028 in the obsolete Julian calendar. Any leap year that starts on Tuesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this leap year occurs in May. Common years starting on Saturday share this characteristic.
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, such as the years 1908, 1936, 1964, 1992, 2020, 2048, 2076, and 2116 in the Gregorian calendar or, likewise, 2004 and 2032 in the obsolete Julian calendar. Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in March and November. Common years starting on Thursday share this characteristic, but also have another in February.
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.
A perpetual calendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the future.
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.
website=
(help)