Conversion between Julian and Gregorian calendars

From Wikipedia, the free encyclopedia - View original article

 
Jump to: navigation, search

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

Conventions[edit]

Conversion table[edit]

These tables are matching the table found in the book by the Nautical almanac offices of the United Kingdom and United States (1961, p. 417, JPEG).

Basic table containing only successive date intervals where differences are constant
or February 29 dates in Julian leap years that are not Gregorian leap years (emphasized rows)
YearJulian
date
Gregorian
date
Difference
in days
−900March 1February 24−8
.........−8
−700February 28February 23−8
−700February 29February 24−8
−700March 1February 25−7
.........−7
−600February 28February 24−7
−600February 29February 25−7
−600March 1February 26−6
.........−6
−500February 28February 25−6
−500February 29February 26−6
YearJulian
date
Gregorian
date
Difference
in days
−500March 1February 24−5
.........−5
−300February 28February 23−5
−300February 29February 24−5
−300March 1February 25−4
.........−4
−200February 28February 24−4
−200February 29February 25−4
−200March 1February 26−3
.........−3
−100February 28February 25−3
−100February 29February 26−3
YearJulian
date
Gregorian
date
Difference
in days
−100March 1February 27−2
.........−2
100February 28February 26−2
100February 29February 27−2
100March 1February 28−1
.........−1
200February 28February 27−1
200February 29February 28−1
200March 1March 10
.........0
300February 28February 280
300February 29March 1
YearJulian
date
Gregorian
date
Difference
in days
300March 1March 2+1
.........+1
500February 28March 1+1
500February 29March 2
500March 1March 3+2
.........+2
600February 28March 2+2
600February 29March 3
600March 1March 4+3
.........+3
700February 28March 3+3
700February 29March 4
YearJulian
date
Gregorian
date
Difference
in days
700March 1March 5+4
.........+4
900February 28March 4+4
900February 29March 5
900March 1March 6+5
.........+5
1000February 28March 5+5
1000February 29March 6
1000March 1March 7+6
.........+6
1100February 28March 6+6
1100February 29March 7
YearJulian
date
Gregorian
date
Difference
in days
1100March 1March 8+7
.........+7
1300February 28March 7+7
1300February 29March 8
1300March 1March 9+8
.........+8
1400February 28March 8+8
1400February 29March 9
1400March 1March 10+9
.........+9
1500February 28March 9+9
1500February 29March 10
YearJulian
date
Gregorian
date
Difference
in days
1500March 1March 11+10
.........+10
1700February 28March 10+10
1700February 29March 11
1700March 1March 12+11
.........+11
1800February 28March 11+11
1800February 29March 12
1800March 1March 13+12
.........+12
1900February 28March 12+12
1900February 29March 13
YearJulian
date
Gregorian
date
Difference
in days
1900March 1March 14+13
.........+13
2100February 28March 13+13
2100February 29March 14
2100March 1March 15+14
.........+14
2200February 28March 14+14
2200February 29March 15
2200March 1March 16+15
.........+15
2300February 28March 15+15
2300February 29March 16


Other intermediate dates (can be inferred from table above)
YearJulian
date
Gregorian
date
Difference
in days
1500March 1March 11+10
.........+10
1582October 4October 14+10
1582October 5October 15+10
1582October 6October 16+10
.........+10
1600February 18February 28+10
1600February 19March 1+10
.........+10
1700February 18February 28+10
1700February 19March 1+10
.........+10
1700February 28March 10+10
1700February 29March 11
YearJulian
date
Gregorian
date
Difference
in days
1700March 1March 12+11
.........+11
1800February 17February 28+11
1800February 18March 1+11
.........+11
1800February 28March 11+11
1800February 29March 12
1800March 1March 13+12
.........+12
1900February 16February 28+12
1900February 17March 1+12
.........+12
1900February 28March 12+12
1900February 29March 13
YearJulian
date
Gregorian
date
Difference
in days
1900March 1March 14+13
.........+13
2000February 15February 28+13
2000February 16March 1+13
.........+13
2100February 15February 28+13
2100February 16March 1+13
.........+13
2100February 28March 13+13
2100February 29March 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.

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. In the table these years are including a February 29 day in the Julian date column, and these dates are listed with emphasized rows. 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.

When converting from Julian to Gregorian, add the number of days from the "Difference" column. If this date falls after the end of the Gregorian month, subtract the number of days of the Gregorian month and increment the month (and year if applicable). IF this date falls before the 1st day of the current month, then decrement the month (and year if applicable) and the number of days in this new month. Sometimes the difference column will be empty if the Julian date to convert is February 29 (it is in an emphasized row), meaning that the correction is not defined as a simple addition (in fact to convert it, first change February 29 into March 1 and add the Difference displayed on the previous row; this will give the equivalent Gregorian day in March, as listed in the Gregorian date column)

When converting from Gregorian to Julian, the process is just reversed, except that you lookup in the table the first date that comes before or at a date listed in the Gregorian column. Then you just need to substract the indicated number of days (counting them in the Gregorian Calendar) from your initial Gregorian date. But sometimes your date to convert will have no difference indicated in the table, and you can only use the date given in the Julian date column, which is a 29 February in the Julian calendar, for years that are leap in the Julian calendar, but not in the Gregorian calendar.

See also[edit]

References[edit]

External links[edit]