I typically work best in the morning. I have my most productive hour the first hour I work. If I'm able to get flow on my project then it will carry me a couple hours into the day. Once I'm pulled out of my flow or I tire, I find it hard to get back in. This is the time I'd like to spend having conversations and/or meetings, with other people helping to spur my imagination.
I can't always control my schedule to this degree, because I work for others, but it's ideal for me.
I suppose it works this way for "morning people".