For me it's the exact opposite. I come in at 9.30am and leave at 6.30pm. Most of my coworkers leave around 4pm, which leaves me 2-2.5 hours at the end of the day to really get shit done.
I'm not a morning person. Understanding and accepting this has helped me manage my time much more effectively.
What you've defined is "core hours". This is the range of time in the day when meetings happen and productivity tends to slow down to a crawl. It sounds like your company's core hours are 9-4. It's fairly standard (some places have core hours being 10a-2p).
I'm not a morning person. Understanding and accepting this has helped me manage my time much more effectively.