The reason behind dark mornings in January can be explained with a formula called the Equation of Time, reveal scientists.
Scientist have explained that if Earth's axis were perpendicular to its orbit instead of tilted, and if its orbit were a circle instead of an ellipse, then the Sun would appear in the same spot in the sky each day and clocks and sundials would always match, the Daily Express reported.
However, as the Earth moves, the two times can be as much as 16 minutes apart, and when the sun reaches its highest point in the sky, it would not always fall at the same time as noon on a clock.
The Earth moves faster in its orbit where it is closest to the Sun, which comes after the winter solstice, and the astronomers have said that the sunrise 'hangs' at the same time just after the winter solstice.
The increased speed pushes solar noon backwards against clock time, and the time stands still for a few days in terms of winter sunrises.