The passes are sold as 2Day and 3Day options. The days quoted are calendar days. This means if you scan a 2Day pass any time on a Monday, the pass will be valid for the rest of that Monday as well as the entire Tuesday. This does, however, mean that if you scan the pass the first time on Monday 16:00, the 2Day pass will still expire end of Tuesday. If you scan the pass the first time on 08:00 on the Monday, it will still expire by the end of Tuesday. The validity period are calendar days.