UTC Time Only?

This is mostly just a question. I was playing around with circadian and I love the idea of it! However, right now it is reading only UTC time. I have the time displayed in my emacs and that is the correct local time. But when setting circadian it was always my dark theme when it should have been the light theme. After playing around I realized it is UTC (which I am in UTC -6). So I would have to set the times to +6 hours from my actual time. It shouldn't be an issue, but wondered if there was a way to set the time circadian uses or where it derives its's time from?