> A quick check of Wikipedia suggests Arabic, Portuguese and Vietnamese, all use number-based systems to name the days of the week, and they are indexed from Su

> A quick check of Wikipedia suggests Arabic, Portuguese and Vietnamese, all use number-based systems to name the days of the week, and they are indexed from Sunday = 1. Vietnamese only numbers the days of the week from Monday to Saturday, with Monday = 2 and Saturday = 7. Sunday has its own name that isn't a number and is always put at the end of the week.