This sounds like what my DH works. I just didn't know it's called a 9-80 schedule.
For a two week period, he works:
1st week - 9 hours (M-TH)
8 hours Friday.
2nd week - 9 hours (M-TH)
Friday off.
If a holiday falls on a Friday off, another day (usually the following Monday) will be the designated holiday day off.
Is this what you are talking about?