Old Style / New Style Date Converter

Convert a date exactly as a historical document writes it — Julian or Gregorian, Lady Day or 1 January, double-dated or numbered — into every other reading of the same day.

The record

Old → New New → Old

Where the record is from

The place that produced the document, not where the person lived. It decides the calendar and the year-start rule.

The date

How the month is written

Month

Day

Year as written

The number on the document. For Russian records before 1700 that is a year counted from the Creation.

The two real days either side

Press a day to load it into the form.

Date	What it is
	The last day before the change
	The first day after it

Modern date (New Style)

22 February 1732 CE

Julian calendar · Friday

As the document writes it

11 February 1731

England, Wales, Ireland & the American colonies

Historical date

11 February 1732 (Julian)

Year corrected, calendar unchanged

Double date

1731/32

The recorded year over the historical one

In England, Wales, Ireland & the American colonies, 11 February 1731 fell under the Julian calendar, with the civil year beginning 25 March (Lady Day).

How this reading was reached

Year start — the civil year in England, Wales, Ireland & the American colonies began 25 March (Lady Day), so the 1731 on the document is historical year 1732.
Calendar — 11 February 1732 in the Julian calendar is Julian Day 2353712, which is 22 February 1732 CE in the modern Gregorian calendar: a difference of +11 days.
Notation — England, Wales, Ireland & the American colonies wrote this year as 1731/32: the recorded year over the historical one.

Eight dates worth trying

Press a row to load it into the form.

As written	Modern	What it shows
	22 February 1732	The double date on a birth record
	25 January 1662	A numbered month, Quaker style
	9 February 1649	Why the execution is dated two ways
	15 February 1748	A birthday people still get wrong
	No such date	A day that never existed
	11 March 1712	The only 30 February ever written
	two readings	An Easter year with two 4 Aprils
	11 October 1699	A year counted from the Creation

What each numbered month means here

Written as	Month
First month	March
Second month	April
Third month	May
Fourth month	June
Fifth month	July
Sixth month	August
Seventh month	September
Eighth month	October
Ninth month	November
Tenth month	December
Eleventh month	January
Twelfth month	February

Under the year beginning 25 March (Lady Day) in England, Wales, Ireland & the American colonies, the first month is March. This mapping changed on 1 January 1752, when the year moved to 1 January.

England, Wales, Ireland & the American colonies: what changed, and when

From	Calendar	Civil year begins	Source
From the start of the covered period	Julian	25 March (Lady Day)	gregorian-adoption-table
From 1 January 1752	Julian	1 January	gregorian-adoption-table
From 14 September 1752	Gregorian	1 January	calendar-act-1750

2 September 1752 was followed by 14 September 1752 — the 11 days between never existed here.

Day of week

Friday

Calendar difference

+11 days

Julian Day Number

2353712

Changeover dates and year-start rules are listed with their sources below.

Need the plain Julian ⇄ Gregorian conversion, with no jurisdiction?

Updated: August 22, 2026

Old Style to New Style date converter. Modern date, corrected year and double date.

An Old Style date converter reads a date the way its own record wrote it and returns the modern date, the corrected year and the double date. It applies the calendar and the year-start rule in force where the document was made, and refuses when a date is impossible or has two equally valid readings.

What Old Style and New Style Dates Are

Old Style (O.S.) and New Style (N.S.) label which dating system a written date belongs to, and two separate things divide the two systems. The first is the calendar: Julian until a given place adopted the Gregorian reform, which by the seventeenth century put the two ten days apart, eleven days apart through the eighteenth century, and thirteen by 1917. The second is the day the civil year rolled over, which across much of Europe was not 1 January. A record can differ from a modern reading on either axis, on both, or on neither, and knowing the calendar tells you nothing about the year start.

In England, Wales, Ireland and the American colonies the civil year opened on 25 March, Lady Day. Sara Read of Loughborough University puts the English and Welsh practice at six centuries, 1155 to 1752, and notes that 25 March was also a quarter day, one of the four dates on which rents and debts fell due. The Calendar (New Style) Act 1750 ended it in two moves, and the section summaries published on legislation.gov.uk still carry the original wording: "The old supputation of the year not to be made use of after Dec. 1751. Year to commence for the future on 1 Jan.", then "The days to be numbered as now until 2d Sept. 1752; and the day following to be accounted 14 Sept. omitting 11 days." One consequence is that 1751 was a stub of a year running 25 March to 31 December, 282 days. The other is that eleven September dates in 1752 were never written on any document.

Scotland had moved a century and a half earlier. The National Records of Scotland records that James VI proclaimed the year should start on 1 January from 1600, and its research guide is explicit that nothing else changed: Scotland kept the Julian calendar for another 152 years and adopted the Gregorian one in 1752 alongside England, Ireland and Wales. Venice is the reverse case. The city took the Gregorian calendar when it arrived in 1582 and kept a year that opened on 1 March until the Republic fell in 1797, so a Venetian February carries a Gregorian day number and the previous year's number, marked more veneto.

Clerks who noticed the clash wrote both years. GENUKI's guide to English dates describes the parish habit: a heading after 24 March naming the year, then a second heading in December giving the split form. An oblique stroke is the usual separator, occasionally a horizontal line set like a fraction, and GENUKI advises against the hyphen, because 1745-6 reads as a span of two years rather than one contested January. A register that says January 1661 records a January its clerk counted in 1661 and a modern reader counts in 1662, and 1661/62 is the notation that says so.

Outside the British Isles the year opened on other days again. France began its year at Easter, which moves, so a French year can hold the same spring date twice or skip it. Russia counted years from the Creation and started them on 1 September until Peter I moved the opening to 1 January in 1700, which left Anno Mundi 7208 four months long; Russian records stayed Julian until 1918. Pisa ran a full year ahead of Florence on the same 25 March start. Quaker registers dropped month names altogether and numbered the months instead, so under a 25 March year the eleventh month is January and the first month is March. From 1752 the first month became January, which makes the numbering depend on the date you are reading rather than on the register as a whole.

How to Read a Record Date With the Converter

The tool asks for the date as written plus one piece of context, then recalculates as you change any field.

1. Pick the direction. Old → New when you are holding the document and want a modern date. New → Old when you have a modern date and want to know how that record would have written it.

2. Choose where the record is from. This is the place that produced the document, not where the person lived: a Scottish parish register kept for an English family follows Scotland's rule. If you do not know, the last option in the list is Julian calendar only, which applies the plain Julian ⇄ Gregorian arithmetic and no year-start correction at all.

3. Say how the month is written. Month names is the default; Numbered months (Quaker style) swaps the month field for a list of ordinals, First month through Twelfth month.

4. Enter the day and the year exactly as they appear on the page. Do not correct the year yourself first — the correction is the thing being calculated. For a Russian record before 1700 the number on the document is counted from the Creation, so 7208 goes in as 7208.

The answer appears as a set of cards. The first is the converted date with its calendar and weekday underneath. "As the document writes it" repeats your entry so you can check it against the page. "Historical date" applies the year correction and leaves the calendar alone. The last card holds the double date, or the style tag when the jurisdiction has one — more veneto, calculus pisanus, calculus florentinus, Anno Mundi. A rule line under the cards names the calendar and the year start that were in force, so the reasoning is visible rather than implied.

Three tiles carry the supporting numbers: the weekday, the calendar difference in days for that century, and the Julian Day Number, which is the unambiguous day count archivists and astronomers use to compare dates across calendars. "How this reading was reached" breaks the conversion into three numbered steps — year start, calendar, notation — with the actual values substituted in.

When a date cannot be read, nothing is converted. The entry stays exactly as you typed it and an explanation replaces the answer: the changeover gap, a short civil year, a date that does not exist in that month, two readings with no way to choose, or one of Sweden's two oddities. Where a sensible next move exists the tool offers it — the two real days either side of a gap are pressable, and a short civil year asks whether you meant the year below or the year above.

Where the Record Is From, and What That Changes

Where the record is from	Civil year began	Calendar, and what to watch for
England, Wales, Ireland & the American colonies	25 March (Lady Day), then 1 January	Julian until 2 September 1752, Gregorian from 14 September 1752. Any date from 1 January to 24 March needs the year raised by one.
Scotland	1 January from 1600	Julian until the same 1752 change. A Scottish January already carries the year a modern reader would give it.
France & New France	Easter, which moves, then 1 January	Julian, then Gregorian. A moving year start can leave one spring date appearing twice in the same year.
Spain, Portugal, the Papal States & Poland–Lithuania	Not modelled before the change, then 1 January	Julian, then Gregorian. No year-start correction is applied for the earlier period, and the tool says so.
Venice	1 March, more veneto, then 1 January	Gregorian from 1582, but with a 1 March year until 1797. January and February carry the previous year's number.
Florence & Tuscany	25 March, calculus florentinus, then 1 January	Julian, then Gregorian. Same start day as England, different jurisdiction and different changeover.
Pisa	25 March a year ahead, calculus pisanus, then 1 January	Julian, then Gregorian. A Pisan year runs a full year ahead of the Florentine one on the same start day.
Prussia (Duchy)	1 January	Julian, Gregorian from 1612. Only the calendar moves here, never the year start.
German Protestant states & Brandenburg	1 January	Julian, then Gregorian. Modelled as a single block; the Catholic bishoprics changed on their own dates and are not covered here.
Denmark & Norway	1 January	Julian, then Gregorian. Only the day shift applies — the year written on the document needs no correction.
Sweden & Finland	1 January	Julian, then Sweden's own calendar, then Julian again, then Gregorian. 29 February 1700 was deleted; 30 February 1712 was inserted.
Russia	1 September, counted from the Creation, then 1 January from 1700	Julian until 1918. Anno Mundi 7208 lasted four months, and years before 1700 are written as Anno Mundi on the document.
Greece	1 January	Julian, then Gregorian. The year start never moves, so the correction is a pure day shift; the timeline panel names the changeover date the tool applies, with its source.
Julian calendar only — jurisdiction not known	Not modelled	Plain Julian ⇄ Gregorian arithmetic with no year-start correction. Use it when the provenance of the document is unknown.

Worked Readings From Real Records

A birth recorded 11 February 1731

George Washington's birth was entered in the family Bible as 11 February 1731, and Americans mark it on 22 February. Set the direction to Old → New, choose England, Wales, Ireland & the American colonies, and enter 11 February 1731. The converter returns 22 February 1732, a Friday, Julian Day Number 2353712, with the calendar difference showing 11 days for that century. The double-date card reads 1731/32. Two corrections are stacked in that one answer: the year rises because February fell before Lady Day, and the day moves because the Julian and Gregorian calendars were eleven days apart in the 1730s. Historians write the recorded year over the corrected one — 11 February 1731/32 — so neither correction gets lost.

The same written date, England or Scotland

Take a record that says 15 January 1661 and convert it twice. With England selected, the answer is 25 January 1662, a Wednesday, historical year 1662, double date 1661/62. With Scotland selected, the answer is 25 January 1661, a Tuesday, historical year 1661, and no double date at all. The day number moves ten days in both cases, because both places were still Julian in 1661. Only the year differs, and it differs because Scotland had moved its year start to 1 January sixty-one years earlier. Nothing on the page of the register tells you which one applies — the provenance of the document does.

A Quaker entry: 15 of the Eleventh month, 1661

Switch How the month is written to Numbered months (Quaker style), keep England, and enter day 15, Eleventh month, year 1661. The converter returns 25 January 1662, Wednesday, double date 1661/62 — the identical answer to 15 January 1661 in month-name notation, because under a year that opens on 25 March the eleventh month is January. Read that entry as November and the record lands two months and one year away from where it belongs. The numbered-month map on the page redraws itself for the jurisdiction and the date, so you can see the whole mapping that applied to the entry in front of you.

Why the execution of Charles I is dated two ways

Contemporary English documents place the execution on 30 January 1648; modern reference works give 1649. Enter 30 January 1648 for England and the converter returns 9 February 1649, a Tuesday, historical year 1649, double date 1648/49. January sat before Lady Day, so the civil year on the warrant was still 1648 while the historical year had already turned. Both dates in circulation are correct readings of the same day, which is why a double date settles the argument in a way either single year cannot.

The dates the converter refuses

Three entries produce no conversion at all. Enter 5 September 1752 for England and the tool reports the changeover gap: 2 September 1752 was followed by 14 September 1752, and the eleven dates between were never written down. It offers the two real days either side to press instead of inventing a day. Enter 10 February 1751 and it reports a short civil year — 1751 ran from 25 March to 31 December, 282 days, so 10 February is not in it — and asks whether you meant 1750 or 1752. Enter 31 April 1700 and it says that month has 30 days in the Julian calendar. In each case the fields keep exactly what you typed, so you can go back to the document and check the reading rather than the arithmetic.

A French date with two possible years

France opened its civil year at Easter, and Easter moves. Enter 4 April 1521 for France and the converter returns two readings side by side: 14 April 1521 and 14 April 1522. The day number is settled — ten days, Julian to Gregorian — but the year is not, because 1521 contained two 4 Aprils under a moving year start and nothing in the date itself distinguishes them. The tool presents both and leaves the choice to your other evidence. Move to 4 April 1520 and a different verdict appears: the civil year 1520 ran 8 April 1520 to 30 March 1521, 357 days, and 4 April is outside it.

Russian and Swedish records

A Russian document dated 1 October 7208 uses Anno Mundi, years counted from the Creation. Enter it with Russia selected and the answer is 11 October 1699, a Sunday, with the style tag naming the era. Peter I moved the Russian year start to 1 January in 1700, and the consequence shows up if you enter 1 May 7208: that civil year ran only 1 September 1699 to 31 December 1699, 122 days. Later Russian dates need the calendar correction alone — 25 October 1917 comes back as 7 November 1917, thirteen days apart, which is why the October Revolution is commemorated in November. Sweden supplies the strangest entry of all: 30 February 1712 converts to 11 March 1712, a Friday. It existed in Sweden and Finland only, in that one year, and the tool rejects it for every other jurisdiction.

Where Old Style Dates Go Wrong

Taking a January, February or early-March date at face value. Those are the only dates that carry a year error under a Lady Day start. A baptism entered as 3 February 1699 in an English register belongs to the historical year 1700, and a marriage entered on 26 March 1699 needs no correction at all.
Assuming the transcriber already fixed it. GENUKI's guide puts the principle plainly: interpretation should always be kept separate from transcription. It also names the failure mode — a single register entry lifted out of its year heading and out of its position in the sequence loses the very context that made the year readable. Check the index's own stated convention before you trust the year in it.
Writing the double date with a hyphen. GENUKI recommends against 1745-6 because it reads as a period spanning two years. The oblique stroke, 1745/6, is the usual form, and a four-digit second element, 1745/1746, removes the last of the ambiguity.
Applying the English rule to a Scottish record. Scotland's year began on 1 January from 1600, so a Scottish January between 1600 and 1752 needs no year correction while an English one does. Getting this backwards moves the event a whole year in either direction.
Reading a Quaker eleventh month as November. Under a 25 March year start it is January, and the first month is March. The mapping changed with the year start in 1752, so the same ordinal means different months depending on when the entry was made.
Adding eleven days to every Old Style date. The gap between the calendars widens by roughly a day a century. It was ten days in the 1600s, eleven through the 1700s, and thirteen in 1917 — which is why the Russian October Revolution is remembered on 7 November.
Treating the calendar and the year start as one switch. Venice ran the Gregorian calendar with a year that opened on 1 March, so a Venetian record dated January or February needs a year correction and no day correction at all. Scotland ran the opposite combination for 152 years.
Repeating the eleven-days riots. Historians treat the 1752 calendar riots as largely or entirely a myth: as IFLScience summarizes the evidence, no contemporary account of anybody rioting over the change survives. The slogan comes from a banner in William Hogarth's 1755 painting An Election Entertainment, which satirises the 1754 election rather than documenting a protest. The reform removed eleven dates from the calendar and nothing from anyone's lifespan.

What This Converter Does Not Do

Regnal years are out of scope. A document dated in the third year of Edward VI names a reign, not a calendar, and resolving it needs a table of accession dates rather than a year-start rule. Bring the calendar date the regnal year resolves to, and the converter will take it from there.

Fourteen jurisdictions are modelled, and several obvious candidates are deliberately absent — Bulgaria, Romania, Serbia, the German Catholic bishoprics and the Dutch provinces among them. In each case the accessible sources disagree about the date of the change, sometimes by years, and a converter that picked one of them without saying so would be worse than one that declines. The Duchy of Prussia is a warning in the other direction: the change belongs to 1612, and the 1610 that appears in some changeover lists is an error.

The French Republican calendar is a different calendar rather than a style of this one. A date in Vendémiaire an II cannot be reached by shifting a year start or adding days, and nothing here will convert it.

Year-start rules are modelled up to 2099. Beyond that the tool says so rather than extrapolating, and falls back to plain arithmetic. It behaves the same way before a jurisdiction's rule is known: enter 11 February 1100 for England and you get 17 February 1100 with the calendar difference of six days for that century, plus a line stating that no year-start correction was applied.

Sweden's twelve-year experiment is handled, but only for Sweden and Finland. 29 February 1700 was deleted there and 30 February 1712 was inserted, and both are rejected for every other jurisdiction, because neither day was ever written anywhere else.

One genuine scholarly disagreement is exposed rather than resolved. Britain Yearly Meeting's own library guide to the Quaker calendar records that the first 24 days of March were read differently by different authorities: Nickalls counted them in the old year, Steel in the new, and Barton argued the Quaker year began on 1 March. For a date in that window the converter names the likelier reading and the alternative, and stops there. The final judgement belongs to whoever has the rest of the evidence — which is to say, to you and the document.

Vocabulary of Old Style Dates

Old Style (O.S.) / New Style (N.S.)

Labels marking which dating system a date belongs to. They can refer to the Julian versus Gregorian calendar, to the old versus new year start, or to both at once.

Lady Day

25 March, the Feast of the Annunciation, and the opening day of the English civil year until the Calendar (New Style) Act 1750 ended the practice. Also one of the four English quarter days for rents and debts.

Civil (legal) year

The year as officially reckoned at the time, running from whatever day that jurisdiction used as its start. This is the year written on the document.

Historical year

The same day counted with a 1 January year start, leaving the calendar untouched.

Double date

A year written in split form, such as 1661/62, showing the civil year and the historical year together. Used for dates between 1 January and the old year start.

more veneto

"In the Venetian manner" — a year that opened on 1 March, used in Venice alongside the Gregorian calendar until 1797. Often abbreviated M.V. after the year.

calculus pisanus / calculus florentinus

The Pisan and Florentine styles, both opening the year on 25 March. The Pisan year runs a full year ahead of the Florentine one.

Anno Mundi

Years counted from the Creation, used in Russian records until Peter I's reform. The year 7208 corresponds to the period covering late 1699.

Numbered months

The Quaker practice of writing months as ordinals instead of names. Under a 25 March year start the first month is March and the eleventh is January.

Julian Day Number

A continuous count of days used by astronomers and archivists. Two dates written in different calendars refer to the same day when their Julian Day Numbers match.

Old Style and New Style Dates: Questions Researchers Ask

What year is a record dated January 1661?

In an English, Welsh, Irish or colonial-American register, January 1661 is the historical year 1662, because the civil year did not turn until 25 March. It is written 1661/62. In a Scottish register it is 1661, with no correction needed.

What does 1731/32 mean on a birth record?

It is a double date. The first number is the civil year the clerk wrote, the second is the historical year the same day belongs to under a 1 January start. It only appears on dates between 1 January and 24 March.

Does Old Style always mean the Julian calendar?

No. Old Style can mean the Julian calendar, the old year start, or both. Scotland kept the Julian calendar from 1600 to 1752 while already starting its year on 1 January. Venice did the reverse, running the Gregorian calendar from 1582 with a year that opened on 1 March until 1797. Because the two axes move independently, the converter asks where the document came from before it applies either one.

Did Scotland use the same Old Style dates as England?

Only partly. The National Records of Scotland records that James VI proclaimed a 1 January year start from 1600, 152 years before England, Wales and Ireland made the same move. Scotland did not adopt the Gregorian calendar then — that came in 1752 for all four. So between 1600 and 1752 a Scottish January date needs the day correction but not the year correction, while an English one needs both.

What does the eleventh month mean in a Quaker register?

Before the 1752 change it means January, because the Quaker numbering followed the civil year that opened on 25 March: first month March, eleventh month January, twelfth month February. After the change the first month became January and the eleventh became November. Select Numbered months (Quaker style) and the converter applies the mapping that was in force on the date you entered, and prints the whole month table underneath so you can check it.

Was there ever a 5 September 1752?

Not in Britain or its colonies. The Calendar (New Style) Act 1750 directed that 2 September 1752 be followed by 14 September 1752, so eleven dates were skipped. The converter refuses those dates and offers the two real days on either side.

How many days do I add to an Old Style date?

It depends on the century, because the gap between the Julian and Gregorian calendars widens by about a day every hundred years. It was ten days for dates in the 1500s and 1600s, eleven through the 1700s, twelve in the 1800s and thirteen from 1900. The converter shows the figure it used as a calendar difference tile, so you can check it against the century you are working in rather than applying a remembered eleven to everything.

How do I know whether a transcription has already been corrected?

Look for the year heading. GENUKI's guide notes that a lone register entry, separated from its year heading and its place in the sequence, is exactly where the meaning gets lost, and it insists that interpretation be kept separate from transcription. Most indexes state their convention somewhere in their front matter; where they do not, a date between 1 January and 24 March that appears without a double date is the one to treat with suspicion. Compare it against a neighboring entry whose date falls after 25 March and the ordering usually gives the answer away.

How should I record an Old Style date in my family tree?

Record what the document says, then record your reading of it separately. GEDCOM writes a date as day, abbreviated month, four-digit year — 15 JAN 1661 — and for a date in the ambiguous window the double date carries both years at once: 15 JAN 1661/62. GENUKI recommends the oblique stroke over the hyphen, since 1661-62 reads as a two-year span. Put the reasoning in a note rather than silently editing the year, so a later researcher can see which correction you applied and why.

Why does the converter ask where the record is from?

Because the year start is a property of the place, not of the calendar. The same written date, 15 January 1661, resolves to 25 January 1662 for an English record and 25 January 1661 for a Scottish one. A converter that only shifts days cannot tell those apart, and neither can it know that a Venetian February belongs to the previous year or that a Russian 7208 is counted from the Creation. Choose the place that produced the document, not where the person lived.

Why does the converter refuse some dates instead of converting them?

Because a number can be produced for 5 September 1752, 10 February 1751 and 31 April 1700, and every one of those numbers would be false. Those dates were never written down: the first sits in the changeover gap, the second in a civil year that had already ended, the third in a month that has thirty days. When a date cannot be read, the tool keeps your entry exactly as typed, explains what is wrong with it, and where possible offers the nearest real dates. A wrong answer in a family tree propagates for years; a refusal sends you back to the document.

Can it handle regnal years like 3 Edw. VI?

No. A regnal year counts from a monarch's accession and needs a table of reigns to resolve, which is a different problem from a year start. Convert the regnal year to a calendar date first, then bring that date here.

Is this Old Style / New Style date converter free to use?

Yes. It runs in your browser at no cost and with no account, in both directions, for as many dates as you need. The eight worked examples on the page are pressable, so you can load a known case, see the answer, and then edit the fields to your own record.

How accurate is the conversion?

The calendar arithmetic is exact and reported as a Julian Day Number, so any answer can be checked against another source that publishes the same figure. The year-start rules and changeover dates come from the sources listed beneath this page, among them the Calendar (New Style) Act 1750 on legislation.gov.uk, the National Records of Scotland guide to the old parish registers, and Britain Yearly Meeting's library guide to the Quaker calendar. Where those sources disagree with each other, the tool declines rather than choosing for you — a French date at an Easter year boundary returns two readings, and a Quaker date in early March names the likelier reading and its alternative.

Why does the British tax year start on 6 April?

The date descends from Lady Day. Jane Frecknall-Hughes of the University of Hull describes the sequence: with the tax year previously tied to 25 March, the eleven days dropped in September 1752 pushed the start of the 1753 tax year to 5 April, and a further adjustment in 1800 moved it on one more day to 6 April, where it has stayed.

What was 30 February 1712?

A real date in Sweden and Finland, and nowhere else, ever. Sweden had planned a gradual move to the Gregorian calendar and dropped 29 February 1700 as the first step, then abandoned the plan and returned to the Julian calendar by inserting an extra day in 1712. Enter it with Sweden & Finland selected and the converter returns 11 March 1712, a Friday. Enter it for any other jurisdiction and it is rejected.

Sources & References

Content verified by the Smart Calculators Team