At my current company I am currently taking PTO to leave early and do volunteer work (~3 hours/week). I had a phone interview and I brought that up that I would like to continue my leaving early for volunteering, and was told that I didn't get any PTO until 90 days. I then asked if I could work extra hours the other days to get to 40 hours. Silence. Ten the HR manager starting stating that I would be salaried and that they go off of the project deadlines not 40 hour weeks.
Good to know I just dodged a bullet working for a company that can't schedule time well.