In this house, the week begins on Sunday
There are some small things that I hold on to from home even though they differ here in England. One of those is which day I treat as the first day of the week.
I remember my confusion at this being different in most of Europe. I discovered it around 2008 or so, when I travelled to Ireland for a debating competition at the end of the year and brought back a calendar with beautiful Irish scenery as a souvenir. Sadly, it was unusable because it began the week on Monday, and that's very confusing as you'd know if you've ever tried reading a calendar that begins the week on a day you're not used to. To avoid this confusion on my UK-region devices today, one of the first things I do when I set them up is set Sunday as the first day of the week.
To this day I don't really get why Monday is the first day of the week in the UK. Throughout the English-speaking Caribbean we use Sunday (despite what Wikipedia says). Americans and Canadians also use Sunday. Presumably we – and most of the Commonwealth, if the map can be believed on this – all inherited this from the UK, which inherited it from Christendom. And historically Christians inherited Sunday as the first day of the week from Jews. When and why did the Brits (and Ozzies and Kiwis) change?