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Use this form to convert dates between the Julian and Gregorian Calendars.

  • To convert a Julian Calendar date to the Gregorian Calendar, key a "day month year" date in the Julian Date textbox.
  • To convert a Gregorian Calendar date to the Julian Calendar, key a "day month year" date in the Gregorian Date textbox.


  1. Key dates in the format "day month year" where day and year are numbers and month is a month name or abbreviation.

    Example: 11 Feb 1731

  2. Day numbers must be one or two digits. This form does not verify that you have entered a valid day number for the given month and year.
  3. Month names must be three-character abbreviations (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec) or the full names (January, February, March, April, May, June, July, August, September, October, November, December). Do not use month numbers.
  4. Year numbers must be three or four digits.
  5. The dates must be in the common era, i.e., 1 Jan 0001 to present.
  6. Set the "Julian New Year's Day" value to the day the year number incremented in the era and locale of interest. Key a day number and a month name or abbreviation.

    The day when the year number increased varied according to the era and locale. In England in 1556, the new year began on March 25, although civil, liturgical, and tax calendars in England may not have all used the same New Year's Day. Meanwhile, in Spain in 1556, the new year began on January 1.