Our core hours are about 8:00 AM to 5:00 PM, but I'm and early riser, plus I like to ride early in the AM. I used to arrive as early as 6:00 AM, but now it's near 7:00 AM. Fortunately my work is flexible, so I always can get started on something for the most part, at my convenience.
Unfortunately, the majority of the work load occurs around noon til 5:00PM, when I'm at an energy low. Again, I can work-shift and plod through those hours, take a nap, and work hard til about 9:00 PM when I take a train home. (I used to take an 8 PM train, allowing me to get to bed and then up earlier).
I'm a bit embarrased to tell people I'm at work from 7 AM until 9 PM, but it is nice to do that early morning commute and have the ability to vary my workload according to my energy levels. The train ride (with my bike) is very relaxing. I also have the opportunity to kick back (within reason) and do some amusing things like posting, etc. when my energy level is low.
I'm not a workaholic, but I can cite the workaholic's prayer: "Thank God it's Monday."