21 year old dating
For example, William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar), in 1688.
Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days, because at the same time the International Date Line was moved, from following Alaska's eastern border with Canada to following its new western border, now with Russia.
Similarly, George Washington is nowadays officially reported as having been born on 22 February 1732, rather than on 11 February 1731/32 (Julian calendar).
There is some evidence that the calendar change was not easily accepted.
For example, the Battle of Blenheim is always given as 13 August 1704.
However confusion occurs when an event involves both.
This change was implemented subsequently in Protestant and Orthodox countries, usually at much later dates.