The weekend is default Saturday and Sunday which is ok for most, but some have a different or in my case longer weekend. I‘d love to be able to customise it, so that I for example can include the Friday and have my whole actual weekend displayed in a darker shade (like in Outlook).
Max has identified an important issue. Being able to customise the weekend days helps not only people with non-standard weekends but also everyone in the Middle East where the weekend is typically Friday/Saturday.