[CookieCrisp]

"A week (or a month) always begins and ends in the same year."

Obviously a week doesn't always begin and end in the same year, but, that a month might not is a new one for me, can someone give me an example?

(Turns out this one was sourced at the bottom, guess it has something to do with years in Roman times - https://en.wikipedia.org/wiki/Gregorian_calendar#Beginning_o... and that a year begins on September 11th in Ethiopia - http://en.wikipedia.org/wiki/Ethiopian_calendar)

[sophacles]

One take on it is better exemplified by saying something like "A day always begins and ends on the same date".

For the purposes of what the calendar says this it's ridiculous to assert that it's a falsehood. For other purposes, it might make perfect sense, for instance a "business day". When I was younger I worked at a bar. We opened at 11am and closed at 2am, and for accounting and legal reasons, the time period of 12am - 2am was the same day as when we opened. Technically we weren't even supposed to serve 21st birthday drinks after midnight, the lawyers said that violated the rules attached to the liquor license, but it wasn't ever enforced. From an accounting point of view - running reports, figuring out how much stock to order, how many people to staff, etc it makes a lot more sense to consider the business day than not.

We had a point of sale system that didn't have a business day notion, and frankly it did nothing but cause problems. Trying to figure out if our Friday and Saturday specials were working was a mess - a very large portion of sales at a bar catering to younger crowds happens after midnight. We were closed on sundays, but still (according to the PoS) realized a pile of income on Sundays. So to do our reports for the accountants we had to do a lot of manual handling of things. To the point where I had to figure out their DB storage and write a bit of code to pull things based on our business hours, just so I could get home before the sun came up when I did a busy weekend close.

Presumably there are similar notions of Month and Week that map to the same sort of reasoning, and there is such a thing as a fiscal year, in which the start and end of year may not be in the same calendar year.

[AnIdiotOnTheNet]

One explanation might be that it depends on how you define "month" in this context. Is it a calendar month, or is it four weeks?

[croes]

Or it's not a standard western calendar

[maxnoe]

It also happens in the japanese calendar, since the year changes when a new emperor ascends the throne and that might not happen on a first of a month

[relativeadv]

I believe the missing context for that statement is timezones and daylight savings can cause it to be untrue.