Editing Friday the 13th (section)

=== Distribution ===
Each 400&nbsp;year [[Gregorian calendar|Gregorian]] [[Solar cycle (calendar)|solar cycle]] contains 146,097&nbsp;days (with 97&nbsp;[[leap year|leap days]]) or exactly 20,871&nbsp;weeks. Each cycle contains the same pattern of days of the week and therefore the same pattern of Fridays that are on the 13th. The 13th&nbsp;day of the month is very slightly more likely to be a Friday than any other day of the week.<ref>{{cite news |author=Bodin, Magnus |date=13 November 1998 |title=About the date+day distribution along the epoch |website=x42 |url=http://x42.com/datelab/daydist.shtml |access-date=30 January 2014}}
</ref><ref>{{cite journal |first1=B.H. |last1=Brown |first2=Raphael |last2=Robinson |name-list-style=amp |year=1933 |title=Solution to problem E36 |journal=[[American Mathematical Monthly]] |volume=40 |issue=10 |page=607|doi=10.2307/2301694 |jstor=2301694 }}
</ref><ref>{{cite book |last=Meeus |first=J. |author-link=Jean Meeus |year=2007 |title=Mathematical Astronomy Morsels IV |page=367}}</ref>

:{| class=wikitable style="margin-left: auto; margin-right: auto; border: none;"
|+ Distribution of the 13th day per weekday over 4,800 months (400 years)
|- style="vertical-align:center; text-align:center"
! Day of the week
! Monday || Tuesday || Wednesday || Thursday || Friday || Saturday || Sunday
|- style="text-align:center;"
! Occurrences
| 685 || 685 || 687 || 684 || '''688''' || 684 || 687
|}

Any month that starts on a Sunday contains a Friday the 13th, and there is at least one Friday the 13th in every calendar year. 
The months with a Friday the 13th are determined by the [[Dominical letter]] (G, F, GF, etc.) of the year. Years which begin on the same day of the week and are of the same type (i.e. [[common year]] or [[leap year]]), will have a Friday the 13th in the same months.

This sequence, given here for 1900–2099, follows a 28-year cycle from 1&nbsp;March 1900 to 28&nbsp;February 2100:

{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
|+ Months with the 13th on a Friday for years from 1900 through 2100
|- style="vertical-align:center;"
! Years during which a Friday the 13th<br/>occurs in the month to the right<br/>(current and subsequent year are marked in bold)
! {{small|Month with<br/>its 13th on<br/>a Friday}}
! {{small|Year length<br/>and weekday of<br/>January the 1st}}
! {{small|Year's<br/>[[Dominical letter|dominical<br/>letter]]}}
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1905, 1911, 1922, 1928, 1933, 1939, 1950, 1956, 1961, 1967, 1978, 1984, 1989, 1995;<br/>{{grey|'''21st-century:'''}} 2006, 2012, 2017, 2023, 2034, 2040, 2045, 2051, 2062, 2068, 2073, 2079, 2090, 2096
| '''January'''
| [[Common year starting on Sunday|365: Sunday]]<br/>[[Leap year starting on Sunday|366: Sunday]]
| '''A'''<br/>'''A'''G
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1903, 1914, 1920, 1925, 1931, 1942, 1948, 1953, 1959, 1970, 1976, 1981, 1987, 1998;<br/>{{grey|'''21st-century:'''}} 2004, 2009, 2015, 2026, 2032, 2037, 2043, 2054, 2060, 2065, 2071, 2082, 2088, 2093, 2099
| '''February'''
| [[Common year starting on Thursday|365: Thursday]]<br/>[[Leap year starting on Thursday|366: Thursday]]
| '''D'''<br/>'''D'''C
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992; 1998;<br/>{{grey|'''21st-century:'''}} 2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099
| '''March'''
| [[Common year starting on Thursday|365: Thursday]]<br/>[[Leap year starting on Wednesday|366: Wednesday]]
| '''D'''<br/>E'''D'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984; 1990;<br/>{{grey|'''21st-century:'''}} 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096
| '''April'''
| [[Common year starting on Monday|365: Monday]]<br/>[[Leap year starting on Sunday|366: Sunday]]
| '''G'''<br/>A'''G'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1904, 1910, 1921, 1927, 1932, 1938, 1949, 1955, 1960, 1966, 1977, 1983, 1988, 1994;<br/>{{grey|'''21st-century:'''}} 2005, 2011, 2016, 2022, 2033, 2039, 2044, 2050, 2061, 2067, 2072, 2078, 2089, 2095
| '''May'''
| [[Common year starting on Saturday|365: Saturday]]<br/>[[Leap year starting on Friday|366: Friday]]
| '''B'''<br/>C'''B'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1902, 1913, 1919, 1924, 1930, 1941, 1947, 1952, 1958, 1969, 1975, 1980, 1986, 1997;<br/>{{grey|'''21st-century:'''}} 2003, 2008, 2014, '''2025''', 2031, 2036, 2042, 2053, 2059, 2064, 2070, 2081, 2087, 2092, 2098
| '''June'''
| [[Common year starting on Wednesday|365: Wednesday]]<br/>[[Leap year starting on Tuesday|366: Tuesday]]
| '''E'''<br/>F'''E'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984, 1990;<br/>{{grey|'''21st-century:'''}} 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096
| '''July'''
| [[Common year starting on Monday|365: Monday]]<br/>[[Leap year starting on Sunday|366: Sunday]]
| '''G'''<br/>A'''G'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1909, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999;<br/>{{grey|'''21st-century:'''}} 2004, 2010, 2021, 2027, 2032, 2038, 2049, 2055, 2060, 2066, 2077, 2083, 2088, 2094, 2100
| '''August'''
| [[Common year starting on Friday|365: Friday]]<br/>[[Leap year starting on Thursday|366: Thursday]]
| '''C'''<br/>D'''C'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;<br/>{{grey|'''21st-century:'''}} 2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097
| '''September'''
| [[Common year starting on Tuesday|365: Tuesday]]<br/>[[Leap year starting on Monday|366: Monday]]
| '''F'''<br/>G'''F'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1905, 1911, 1916, 1922, 1933, 1939, 1944, 1950, 1961, 1967, 1972, 1978, 1989, 1995,  2000;<br/>{{grey|'''21st-century:'''}} 2006, 2017, 2023, 2028, 2034, 2045, 2051, 2056, 2062, 2073, 2079, 2084, 2090
| '''October'''
| [[Common year starting on Sunday|365: Sunday]]<br/>[[Leap year starting on Saturday|366: Saturday]]
| '''A'''<br/>B'''A'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1903, 1908, 1914, 1925, 1931, 1936, 1942, 1953, 1959, 1964, 1970, 1981, 1987, 1992, 1998;<br/>{{grey|'''21st-century:'''}} 2009, 2015, 2020, 2026, 2037, 2043, 2048, 2054, 2065, 2071, 2076, 2082, 2093, 2099
| '''November'''
| [[Common year starting on Thursday|365: Thursday]] <br/> [[Leap year starting on Wednesday|366: Wednesday]]
|style="text-align:center"| '''D''' <br/>E'''D'''
|- style="text-align:center;" 
|style="text-align:left;"| {{grey|'''20th-century:'''}} 1901, 1907, 1912, 1918, 1929, 1935, 1940, 1946, 1957, 1963, 1968, 1974, 1985, 1991, 1996;<br/>{{grey|'''21st-century:'''}} 2002, 2013, 2019, 2024, 2030, 2041, 2047, 2052, 2058, 2069, 2075, 2080, 2086, 2097
| '''December'''
| [[Common year starting on Tuesday|365: Tuesday]]<br/>[[Leap year starting on Monday|366: Monday]]
| '''F'''<br/>G'''F'''
|}