Common year starting on Friday

A common year starting on Friday is any non-leap year (i.e. a year with 365 days) 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,[1] 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.

Calendars

Calendar for any common year starting on Friday,
presented as common in many English-speaking areas

01 02
03 04 05 06 07 08 09
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31  
01 02 03 04 05 06
07 08 09 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28  
 
01 02 03 04 05 06
07 08 09 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31  
 
01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30
 
01
02 03 04 05 06 07 08
09 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31  
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30  
 
01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
 
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31  
 
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30  
 
01 02
03 04 05 06 07 08 09
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31  
01 02 03 04 05 06
07 08 09 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30  
 
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31  
 

ISO 8601-conformant calendar with week numbers for
any common year starting on Friday (dominical letter C)

01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
 
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30  
 
01 02 03 04
05 06 07 08 09 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31  
 
01 02 03
04 05 06 07 08 09 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
 
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
 
01 02
03 04 05 06 07 08 09
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31  
01
02 03 04 05 06 07 08
09 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31  
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30  
 
01 02 03 04 05 06 07
08 09 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31  
 
01 02 03 04 05 06
07 08 09 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30  
 
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30  
 
01 02 03 04 05
06 07 08 09 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31  
 

This is the only year type where the nth "Doomsday" (this year Sunday) is not in ISO week n; it is in ISO week n-1.

Applicable years

Gregorian Calendar

In the (currently used) Gregorian calendar, the fourteen types of year (seven common, seven leap) repeat in a 400-year cycle (20871 weeks). Forty-three common years per cycle or exactly 10.75% start on a Friday. The 28-year sub-cycle does only span across century years divisible by 400, e.g. 1600, 2000, and 2400.

Gregorian common years starting on Friday[1]
Decade 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th
16th century prior to first adoption (proleptic) 1593 1599
17th century 1610 1621 1627 1638 1649 1655 1666 1677 1683 1694 1700
18th century 1706 1717 1723 1734 1745 1751 1762 1773 1779 1790
19th century 1802 1813 1819 1830 1841 1847 1858 1869 1875 1886 1897
20th century 1909 1915 1926 1937 1943 1954 1965 1971 1982 1993 1999
21st century 2010 2021 2027 2038 2049 2055 2066 2077 2083 2094 2100

Julian Calendar

In the now-obsolete Julian calendar, the fourteen types of year (seven common, seven leap) repeat in a 28-year cycle (1461 weeks). A leap year has two adjoining dominical letters (one for January and February and the other for March to December, as 29 February has no letter). This sequence occurs exactly 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 4, 15 and 26 of the cycle are common years beginning on Friday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Friday.

Julian common years starting on Friday
Decade 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th
15th century 1406 1417 1423 1434 1445 1451 1462 1473 1479 1490
16th century 1501 1507 1518 1529 1535 1546 1557 1563 1574 1585 1591
17th century 1602 1613 1619 1630 1641 1647 1658 1669 1675 1686 1697
18th century 1703 1714 1725 1731 1742 1753 1759 1770 1781 1787 1798
19th century 1809 1815 1826 1837 1843 1854 1865 1871 1882 1893 1899
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

References

  1. ^ a b c Robert van Gent (2017). "The Mathematics of the ISO 8601 Calendar". Utrecht University, Department of Mathematics. Retrieved 20 July 2017.
101

Year 101 (CI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Traianus and Paetus (or, less frequently, year 854 Ab urbe condita). The denomination 101 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

1025

Year 1025 (MXXV) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1109

Year 1109 (MCIX) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1182

Year 1182 (MCLXXXII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1227

Year 1227 (MCCXXVII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1305

Year 1305 (MCCCV) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1311

Year 1311 (MCCCXI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1350

Year 1350 (MCCCL) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1361

Year 1361 (MCCCLXI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1367

Year 1367 (MCCCLXVII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1417

Year 1417 (MCDXVII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1451

Year 1451 (MCDLI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1546

Year 1546 (MDXLVI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.

1582

1582 (MDLXXXII)

was a common year starting on Monday of the Julian calendar, the 1582nd year of the Common Era (CE) and Anno Domini (AD) designations, the 582nd year of the 2nd millennium, the 82nd year of the 16th century, and the 3rd year of the 1580s decade. As of the start of 1582, the Gregorian calendar was

10 days ahead of the Julian calendar, which had previously been the universally accepted calendar in Christian nations. However, this year saw the beginning of the Gregorian Calendar switch, when the Papal bull known as Inter gravissimas introduced the Gregorian calendar, adopted by Spain, Portugal, the Polish–Lithuanian Commonwealth and most of present-day Italy from the start. In these countries, the year continued as normal until Thursday, October 4. However, the next day became Friday, October 15 (like a common year starting on Friday), in those countries (France followed two months later, letting Sunday, December 9 be followed by Monday, December 20). Other countries continued using the Julian calendar for decades or, in some cases, centuries. The complete conversion of the Gregorian calendar was not entirely done until 1923. In the Proleptic Gregorian calendar, 1582 is a common year starting on Friday (link will display the full calendar).

1734

1734 (MDCCXXXIV)

was a common year starting on Friday of the Gregorian calendar and a common year starting on Tuesday of the Julian calendar, the 1734th year of the Common Era (CE) and Anno Domini (AD) designations, the 734th year of the 2nd millennium, the 34th year of the 18th century, and the 5th year of the 1730s decade. As of the start of 1734, the Gregorian calendar was

11 days ahead of the Julian calendar, which remained in localized use until 1923.

1999 in Bangladesh

1999 (MCMXCIX)

was a common year starting on Friday of the Gregorian calendar, the 1999th year of the Common Era (CE) and Anno Domini (AD) designations, the 999th year of the 2nd millennium, the 99th year of the 20th century, and the 10th and last year of the 1990s decade.

The year 1999 was the 28th year after the independence of Bangladesh. It was also the fourth year of the first term of the Government of Sheikh Hasina.

1 BC

Year 1 BC was a common year starting on Friday or Saturday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a leap year starting on Thursday of the Proleptic Julian calendar. It is also a leap year starting on Saturday, in the Proleptic Gregorian calendar. At the time, it was known as the Year of the Consulship of Lentulus and Piso (or, less frequently, year 753 Ab urbe condita). The denomination 1 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. The following year is 1 AD in the widely used Julian calendar, which does not have a "year zero".

2021

2021 (MMXXI)

will be a common year starting on Friday of the Gregorian calendar, the 2021st year of the Common Era (CE) and Anno Domini (AD) designations, the 21st year of the 3rd millennium, the 21st year of the 21st century, and the 2nd year of the 2020s decade.

34 BC

Year 34 BC was either a common year starting on Friday, Saturday or Sunday or a leap year starting on Friday or Saturday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a common year starting on Friday of the Proleptic Julian calendar. At the time, it was known as the Year of the Consulship of Antonius and Libo (or, less frequently, year 720 Ab urbe condita). The denomination 34 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

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