One of the funny things about historical dates is that everything's pretty consistent now, but if you try to give a date in the past, starting about a hundred years ago, suddenly it can start getting confusing what date everyone thought it was at that time.

(By the way, the correct way to avoid this trouble is to use a "proleptic calendar", which is a calendar projected back into the past, even before it was conceived. This is so obviously the right way to do date accounting that everyone does it, without a second thought (people in BC didn't even know there was a C to be B!). However, it won't tell you what date was printed on newspapers and stuff in the place at the time.)

Example: https://en.wikipedia.org/wiki/Old_Style_and_New_Style_dates

To quote:

> Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, they refer to the change from the Julian calendar to the Gregorian calendar as enacted in various European countries between 1582 and 1923. 

This is not so long ago!

To continue to quote:

> In England, Wales, Ireland and Britain's American colonies, there were two calendar changes, both in 1752. The first adjusted the start of a new year from 25 March (Lady Day, the Feast of the Annunciation) to 1 January, a change which Scotland had made in 1600. The second discarded the Julian calendar in favour of the Gregorian calendar, skipping 11 days in the month of September to do so.[2][3] To accommodate the two calendar changes, writers used dual dating to identify a given day by giving its date according to both styles of dating.

The first time I learned about this my brain basically blue screened for a moment while I pondered what it would mean for the start of a new year to be the 25th of March.

(It means that day is when they increment the year number.

Which is really weird! In the current system I think of days as being contained in months as being contained in years! But you don't have to do that, as they've just shown lmao.)