Yes - Monday through Friday are weekdays, and Saturday and Sunday are weekend days. However, hotels consider Fridays and Saturdays to be weekend nights. The rates are usually higher on weekends in resort areas, and lower on weekends in big cities.
When I leave work on Friday afternoon, I consider that the start of my weekend. So Friday & Saturday are my weekend nights. I don't consider Sunday night a weekend night because I have to get up early on Monday!
100% standard among hotels. Walt Disney World was very late to the party, only differentiating between weekend and weekday rates in the last year or two.