This year our term dates were set so we were back on 2 Jan. No-one wanted that, not even as an inset day, so we agreed we'd run twilight training sessions most Tuesdays for 1.5 hours during the autumn term (because by coincidence all our p-r staff work on a Tuesday). Staff could choose which sessions they wanted and there were a wide variety of topics.
Full-time staff to do three sessions, part-time 2 sessions.
OMG, the drama it caused. Ft is 6.5 hours for aday so they were getting 2 "free hours". Part-time hours vary quite a lot, but it wasn't really feasible to say OK Anne you need to do 87 minutes and Joan you need 182 to get the same benefit. All the part-timers would have worked less then their full inset day but some would have got more "free time" than others.
We have the same situation in 2019 and will probably work an inset day on 2 Jan to save the aggravation, unless there's a better way?
The head tried to do a nice thing for staff and boy did it backfire.