Enrichment · Passion Projects · Family history

February 11, 1731
is February 22, 1732.

Old records count days and years differently. Type the date as the record has it; the converter gives the same day in the other calendar, its weekday and the way historians write it.

Convert a dateWhat you get

The historical date format converter

The worked example is a family Bible birth entry for 11 February 1731/2. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
The same day in the other calendar, the weekday, the gap between calendars, the double-dated form, the ISO date and the Julian Day Number, with the week around it in both calendars. It prints as a note for your research file.
Who it is for
Family historians reading parish registers and Bibles, history students working with primary sources, and families researching their own records.
Format
Browser converter for a phone, tablet or computer, by touch or keyboard. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Type the date as written.
  2. Pick the calendar it uses.
  3. Mark a March 25 year start.
  4. Read both dates.
  5. Record them as O.S. and N.S.

Convert a date

How old dates are converted

Two calendars, two ways of starting the year.

The worked example: a birth entry dated 11 February 1731/2As written11 Feb 1731year begins Mar 25Modern year11 Feb 1732Julian, Jan 1 yearDay count2,353,712Julian Day NumberGregorianFeb 22, 1732FridayThe worked example: a birth entry dated 11 February 1731/2As written11 Feb 1731year begins Mar 25Modern year11 Feb 1732Julian, Jan 1 yearDay count2,353,712Julian Day NumberGregorianFeb 22, 1732Friday
The record’s year is moved to a January start, the Julian date becomes a day count, and the count is read back as a Gregorian date.

Julian and Gregorian

The Julian calendar adds a leap day every fourth year, which runs slightly fast. The Gregorian calendar of 1582 drops three leap days every four centuries. Catholic countries switched in 1582; Britain and its colonies in 1752, when September 2 was followed by September 14; others as late as the twentieth century. The gap grew from 10 days to 11 in 1700, 12 in 1800 and 13 in 1900.

Two New Year’s Days

Before 1752, English and colonial legal records began the year on March 25, so a date between January 1 and March 24 belongs to the next year by today’s count. Historians write both years, 1731/32. George Washington was born on 11 February 1731/2 Old Style, the day now written February 22, 1732.

Sources

  1. Library of Congress. The Julian and Gregorian calendars, and Old Style and New Style dates (loc.gov).
  2. National Archives (U.S.). Calendar changes and dating historical documents (archives.gov).
  3. U.S. Naval Observatory. Julian Date and the conversion of calendar dates (aa.usno.navy.mil).
  4. Richards, E. G. (2013). Calendars. In S. E. Urban & P. K. Seidelmann (Eds.), Explanatory Supplement to the Astronomical Almanac (3rd ed.). University Science Books.

The converter follows each calendar’s rules; whether a particular record used Old or New Style depends on the place and date, which the record and its context must settle. Your entries stay in this browser. Support: team@caveatacademic.com.