DH is salary and he is allowed the flexibility to leave early, duck out for a few hours, etc to make a school event, Dr. appointment, etc. He more than makes up for it by often being at work very late when he is in town and he travels about 80% of the time. Most weeks he is gone Monday morning until late (8:00 or 9:00) Friday night. Sometimes he has to leave on Sunday or come home on Saturday. He misses a HUGE amount of school events, and has to put off follow up care at the doctor for high blood pressure, etc. because of the travel so his boss is very willing to be flexible to let him to what he needs to do in the short amount of time he is home.
When I worked as a librarian, I could generally take off whenever I needed/wanted UNPAID and only if I could get someone else to come in for me. We were all part time with busy lives and we al tried to cover for each otehr as much as possible. Often we were able to just trade days so that everyone still got a good paycheck as well.