Conversion between Julian and Gregorian calendars

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The tables below list equivalent dates in the Julian and Gregorian calendars. Years are given in astronomical year numbering.

This is a visual example of the official date change from the Julian calendar to the Gregorian

Conventions[edit]

  • Within these tables, January 1 is always the first day of the year.
  • The Gregorian calendar did not exist before October 15, 1582. Gregorian dates before that are proleptic, that is, using the Gregorian rules to reckon backward from October 15, 1582.
  • Years are given in astronomical year numbering.
  • Augustus corrected errors in the observance of leap years by omitting leap days until 8. Julian calendar dates before 8 are proleptic, and do not necessarily match the dates actually observed in the Roman Empire (Nautical almanac offices of the United Kingdom and United States, 1961, p. 411).

Conversion table[edit]

This table is taken from the book by the Nautical almanac offices of the United Kingdom and United States (1961, p. 417, JPEG).

Year Julian date Gregorian date Difference
−500 March 5 February 28
−500 March 6 March 1 −5
−300 March 3 February 27 −5
−300 March 4 February 28
−300 March 5 March 1 −4
−200 March 2 February 27 −4
−200 March 3 February 28
−200 March 4 March 1 −3
−100 March 1 February 27 −3
−100 March 2 February 28
−100 March 3 March 1 −2
100 February 29 February 27 −2
100 March 1 February 28
100 March 2 March 1 −1
200 February 28 February 27 −1
200 February 29 February 28
200 March 1 March 1 0
300 February 28 February 28 0
300 February 29 March 1
300 March 1 March 2 1
Year Julian date Gregorian date Difference
500 February 28 March 1 1
500 February 29 March 2
500 March 1 March 3 2
600 February 28 March 2 2
600 February 29 March 3
600 March 1 March 4 3
700 February 28 March 3 3
700 February 29 March 4
700 March 1 March 5 4
900 February 28 March 4 4
900 February 29 March 5
900 March 1 March 6 5
Year Julian date Gregorian date Difference
1000 February 28 March 5 5
1000 February 29 March 6
1000 March 1 March 7 6
1100 February 28 March 6 6
1100 February 29 March 7
1100 March 1 March 8 7
1300 February 28 March 7 7
1300 February 29 March 8
1300 March 1 March 9 8
1400 February 28 March 8 8
1400 February 29 March 9
1400 March 1 March 10 9
1500 February 28 March 9 9
1500 February 29 March 10
1500 March 1 March 11 10
Year Julian date Gregorian date Difference
1582 October 4 October 14 10
1582 October 5 October 15 10
1582 October 6 October 16 10
1700 February 18 February 28 10
1700 February 19 March 1 11
1700 February 28 March 10 11
1700 February 29 March 11 11
1700 March 1 March 12 11
1800 February 17 February 28 11
1800 February 18 March 1 12
1800 February 28 March 11 12
1800 February 29 March 12 12
1800 March 1 March 13 12
1900 February 16 February 28 12
1900 February 17 March 1 13
1900 February 28 March 12 13
1900 February 29 March 13 13
1900 March 1 March 14 13
2100 February 15 February 28 13
2100 February 16 March 1 14
2100 February 28 March 13 14
2100 February 29 March 14 14

Using the tables[edit]

Dates near leap days that are observed in the Julian calendar but not in the Gregorian are listed in the table. Dates near the adoption date in some countries are also listed. For dates not listed, see below.

The usual rules of algebraic addition and subtraction apply; adding a negative number is the same as subtracting the absolute value, and subtracting a negative number is the same as adding the absolute value.

If conversion take you past a February 29 that exists only in the Julian calendar, then February 29 is counted in the difference. When February 29 is skipped in the Gregorian calendar, it becomes March 1, March 1 becomes March 2, ..., and February 28 becomes February 29 or March 1.

No guidance is provided about conversion of dates before March 5, -500, or after March 28, 2100 (both being Julian dates).

Years not evenly divisible by 100, or evenly divisible by 400[edit]

For unlisted dates, find the date in the table closest to, but earlier than, the date to be converted. Be sure to use the correct column. If converting from Julian to Gregorian, add the number from the "Difference" column. If converting from Gregorian to Julian, subtract. When adding, remember every year that this section applies to is a leap year in both calendars so February 29 must be included in the addition if applicable.

Years evenly divisible by 100 and not divisible by 400[edit]

Every year that fits into this section is a Julian leap year and a Gregorian common year. For unlisted dates, find the date in the table closest to, but earlier than, the date to be converted. Be sure to use the right column. If converting from Julian to Gregorian, add the number from the "Difference" column, but ignore February 29 if applicable. If converting Gregorian to Julian subtract but ignore February 29 if applicable.

See also[edit]

References[edit]

  • Nautical almanac offices of the United Kingdom and United States. (1961). Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac (pp. 410–8 ). London: H. M. Stationery Office.

External links[edit]