Sunrise has been getting a little bit later every morning since the solstice although the hours of daylight have been increasing. Things are complicated by the way that the Earth has two cycles of motion. It spins on its axis but at the same time it moves around the Sun. This means that it has to rotate through 361 degrees to get to the point where the Sun is the same height in the sky. Also the Earth follows an elliptical orbit around the Sun. At the moment the Earth is closer to the Sun than at other times of the year (see diagram on http://www.jwstelly.org/TheCalendar/Gregoria nCalendar.html According to http://www.bbc.co.uk/news/magazine-30549149 this means that one rotation of the Earth lasts 24 hours and 30 seconds at the moment. I think I'll need to draw some diagrams to get to the bottom of this. And that's before you chuck in the tilt of the Earth. But the darkest morning will be Jan 2nd and then it gets better.