Hyper Stone Question

Infliction - Raging Tide

Last night at about 7:30 my time, I used hyper stones for an hour of aoe grinding. I didn't use any the day before(the 18th), so I thought I would be able to do 2 sessions yesterday, but I could only do 1. I'm trying right now to start another(4:00), and it says I can only start 1 session a day, does that mean I have to wait until 7:30 or is it just overall messed-up?