Earth is at its closest to the sun in the beginning of January and the distance is largest in the beginning of July. Therefore the period between the equinoxes that contain January is shorter than the rest of the year (i.e. the period between autumn and spring equionox in the northern hemisphere). Shorter distance to the sun means greater gravity force and that gives more speed. More speed in January makes the dark period of the year shorter when you live north of the equator and longer if you live south of the equator.

But try to imagine the effects if you divide the year into 4 parts, not only dark and light but also the periods in between, spring and autumn. If the axis of the Earth had pointed so that winter solstice also was located at the beginning of January, then there would have been no difference in length between the periods of 'spring' and 'autumn'.

What exactly do I mean with 'spring' and 'autumn' and how long are these periods? Let me explain on next page.