Both.

We have "core hours" of 10 - 4, and so long as people are here between these ( when meetings are scheduled ), it isn't very important when people come or go. We need to be here for eight hours, and to be productive. I like to come in between 8 and 8:30, which balances my "not a morning person" -ness against my desire to get out at a reasonable time. When I used to drive, I would let things like freeway traffic stress me out.

I usually make it here at the same time whether I drive or cycle, but trying to make that happen in a car is much more stressful. Occasionally, traffic is especially foul, and I would come in ten minutes later than I planned. On the bike, I get up a little earlier than normal ( because the commute is up hill ) and know I have some time to spare; I also know that traffic and parking issues can't slow me down much. So I don't stress about making it in on time.