Unfortunately there is no regular schedule but there are several sources that post when it’s activated. The SSTV events are done by the Russians and they don’t announce them far in advance, sometimes only a few days, a week, maybe two weeks out if we’re lucky. There is also the issue with scheduling lower priority stuff like ham radio, it can get cancelled for higher priority stuff like science.
With that said these are the resources you can follow to be notified of an event.
73, John Brier KG4AKV