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 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 AD 8. Julian calendar dates before March AD 4 are proleptic, and do not necessarily match the dates actually observed in the Roman Empire.
Conversion table This table is taken from the book by the Nautical almanac offices of the United Kingdom and United States originally published in 1961. Year Julian date Gregorian date Difference −500March 5February 28 −500March 6March 1−5 −300March 3February 27−5 −300March 4February 28 −300March 5March 1−4 −200March 2February 27−4 −200March 3February 28 −200March 4March 1−3 −100March 1February 27−3 −100March 2February 28 −100March 3March 1−2 100February 29February 27−2 100March 1February 28 100March 2March 1−1 200February 28February 27−1 200February 29February 28 200March 1March 10 300February 28February 280 300February 29March 1 300March 1March 21 Year Julian date Gregorian date Difference 500February 28March 11 500February 29March 2 500March 1March 32 600February 28March 22 600February 29March 3 600March 1March 43 700February 28March 33 700February 29March 4 700March 1March 54 900February 28March 44 900February 29March 5 900March 1March 65 Year Julian date Gregorian date Difference 1000February 28March 55 1000February 29March 6 1000March 1March 76 1100February 28March 66 1100February 29March 7 1100March 1March 87 1300February 28March 77 1300February 29March 8 1300March 1March 98 1400February 28March 88 1400February 29March 9 1400March 1March 109 1500February 28March 99 1500February 29March 10 1500March 1March 1110 Year Julian date Gregorian date Difference 1582October 4October 1410 1582October 5October 1510 1582October 6October 1610 1700February 18February 2810 1700February 19March 111 1700February 28March 1011 1700February 29March 1111 1700March 1March 1211 1800February 17February 2811 1800February 18March 112 1800February 28March 1112 1800February 29March 1212 1800March 1March 1312 1900February 16February 2812 1900February 17March 113 1900February 28March 1213 1900February 29March 1313 1900March 1March 1413 2100February 15February 2813 2100February 16March 114 2100February 28March 1314 2100February 29March 1414
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.
If conversion takes you past a February 29 that exists only in the Julian calendar, then February 29 is counted in the difference. Years affected are those which divide by 100 without remainder but do not divide by 400 without remainder (e.g., 1900 and 2100 but not 2000).
No guidance is provided about conversion of dates before March 5, -500, or after February 29, 2100 (both being Julian dates).
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.
See also Revised Julian calendar
References
External links