Scheduling

Ok, so I am fortunate enough to work in an office that goes to a 4 day work week for the summer. But here's the catch, if we have groups in, then obviously we don't all take the day off. Well, today is the first day of the first week of the summer schedule, so instead of taking 5 days to work 40 hours, you split 40 hours into 4 days. I'm bad at math, but this is a simple concept to me. Apparently though, I am a genius because everyone else can't seem to figure out when to come to work???