Type your name, then paint the dates you can't make (red) or would rather not (amber) — tap to cycle a single day, or press and drag to paint a stretch. Hit Save my dates when you're done. The best dates for the whole class update live on the right.
Painting works with mouse and finger — on a phone, the clear strip to the right of each month is for scrolling. Your entry is stored under your name; saving again replaces it. v1.1.0