Conversion between Julian and Gregorian calendars
The tables below list equivalent dates in the Julian and Gregorian calendars. Years are given in astronomical year numbering.
Conventions
- 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 recon backward from October 15, 1582.
- Augustus corrected errors in the observance of leap years by omitting leap days until A.D. 8. Julian calendar dates before A.D. 8 are proleptic, and do not necessarily match the dates actually observed in the Roman Empire.
Astronomical years -500 to +300
| Year | Julian Date | Gregorian Date | No. days Julian is behind |
| -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 |
A.D. 300 March 1 to 1582 October 4/14
| Year | Julian Date | Gregorian Date | No. days Julian is behind |
| 300 | February 29 | March 1 | |
| 300 | March 1 | March 2 | 1 |
| 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 |
| 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 |
| 1582 | October 4 | October14 | 10 |
1582 October 5/15 to 2100 February 28/March 13
| Year | Julian Date | Gregorian Date | No. days Julian is behind |
| 1582 | October 5 | October 15 | 10 |
| 1582 | October 6 | October 16 | 10 |
| 1700 | February 18 | February 28 | 10 |
| 1700 | February 19 | March 1 | 10 |
| 1700 | February 28 | March 10 | 10 |
| 1700 | February 29 | March 11 | |
| 1700 | March 1 | March 12 | 11 |
| 1800 | February 17 | February 28 | 11 |
| 1800 | February 18 | March 1 | 11 |
| 1800 | February 28 | March 11 | 11 |
| 1800 | February 29 | March 12 | |
| 1800 | March 1 | March 13 | 12 |
| 1900 | February 16 | February 28 | 12 |
| 1900 | February 17 | March 1 | 12 |
| 1900 | February 28 | March 12 | 12 |
| 1900 | February 29 | March 13 | |
| 1900 | March 1 | March 14 | 13 |
| 2100 | February 15 | February 28 | 13 |
| 2100 | February 16 | March 1 | 13 |
| 2100 | February 28 | March 13 | 13 |
Using the tables
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.
Years not evenly divisible by 100, or evenly divisible by 400
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
Every year that fit 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.
References
- 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.