Dates and Days

Day of the week

What day of the week was any date

The weekday is the easy part and it has never been interrupted: when Europe changed calendars, days were dropped from the calendar and not from the week. Britain went to bed on Wednesday 2 September 1752 and woke on Thursday the 14th. So the harder question is what a date was actually called where you are asking about — and this answers both.

Weekday— Day of year— ISO week— Called there— From today—
—
Where and when the calendar changed — the calendar jumped; the week did not
WhereLast Julian dateFirst Gregorian dateDates skippedWeekday ran

The eleven days that never existed

The Julian calendar made every fourth year a leap year with no exception, which is about eleven minutes a year too generous. Over sixteen centuries that accumulated into ten days of drift against the seasons, and in 1582 the Gregorian reform removed them and added the century rule that keeps it from happening again. Catholic Europe changed that October: Thursday the 4th was followed by Friday the 15th.

Everyone else took their time. Britain and its colonies waited until 1752, by which point the gap was eleven days, and went from Wednesday 2 September straight to Thursday the 14th. Russia held out until 1918 and skipped thirteen. Greece was last in 1923. So for any date between 1582 and 1923, “what was the date” genuinely depends on where you are asking about, which is what the selector above is for.

The one thing that never varied is the weekday. No country dropped a day of the week; they dropped date labels. That is why the table shows every switch running from one weekday to the next with nothing missing, and why the weekday answer above needs no region at all.

Old Style, New Style, and why Washington has two birthdays

England had a second quirk: until 1752 the civil year began on 25 March, not 1 January. So a date in January, February or most of March carried what we would now call the previous year’s number. George Washington was born on 11 February 1731 by the calendar in use where he lived, and on 22 February 1732 by ours — same day, two labels, and the convention of writing it “1731/32” exists precisely because contemporaries found it confusing too.

Ask about a pre-1752 date with Britain selected and both labels are given, including the older year number where it applies. Historians call the modern label New Style and the contemporary one Old Style, and a date quoted without saying which can be out by both eleven days and a year.

Sweden is not in the table, deliberately

Sweden decided to convert gradually by omitting every leap day from 1700 to 1740, got as far as skipping one, then forgot, and spent twelve years on a calendar that matched nobody — a day ahead of the Julian world and ten behind the Gregorian one. It gave up in 1712 by adding a 30 February to get back to Julian, then switched properly in 1753. No single pair of dates describes that honestly, so it is left out rather than approximated.

Questions

What day of the week was I born?
Enter your date of birth above and the weekday is exact — the weekday cycle has never been interrupted anywhere, so there is no ambiguity and no convention to choose. What can be ambiguous is the DATE itself, but only for dates before 1923, and only if you are asking about a country that had not yet adopted the Gregorian calendar.
Why did Britain skip eleven days in 1752?
Because the Julian calendar made every fourth year a leap year with no exception, which is about eleven minutes a year too generous, and by 1752 that had accumulated into an eleven-day drift against the seasons. The Gregorian reform of 1582 removed the accumulated error and added the century rule that prevents it recurring. Britain adopted it 170 years late, so Wednesday 2 September 1752 was followed by Thursday 14 September. The dates 3 to 13 September 1752 never existed in Britain or its colonies.
Did anyone lose a day of the week?
No, and this is the part most often got wrong. Days were dropped from the CALENDAR, not from the WEEK. Every switch in the table runs from one weekday directly to the next with nothing missing. That is why the weekday answer above needs no region selected: it is the same everywhere, for every date, regardless of which calendar anyone was using at the time.
Why do some historical dates have two different years?
Because England began its civil year on 25 March until 1752, so dates in January, February and most of March carried the previous year's number. George Washington was born 11 February 1731 by the calendar where he lived and 22 February 1732 by ours — one day, two labels, differing by both eleven days and a year. The convention of writing such dates as 1731/32 exists because contemporaries found it confusing as well. Historians call the modern label New Style and the contemporary one Old Style.
Why is Sweden missing from the table?
Because no single pair of dates describes what Sweden did. It decided to convert gradually by omitting every leap day from 1700 to 1740, skipped one, then forgot, and spent twelve years on a calendar that agreed with nobody — one day ahead of the Julian world and ten days behind the Gregorian one. In 1712 it gave up and added a 30 February to return to the Julian calendar, then converted properly in 1753. Approximating that with a single switch date would be a tidier answer and a false one.