Right now, the sun peeks in the window when I get up at 7, but it's bright enough to trigger my 'daylight' reflexes for about an hour and a half before that. And by next weekend, daylight will start so early that DST won't have a meaningful impact on that end of the day - but it will make me leave work in full daylight, even on days when I work late :)
For natural reasons, I work on suppressing my 'daylight' reflexes in the morning in spring. And I have very thick curtains.