I asked people if they know why the days get shorter in the summer, and they all replied, you mean the opposite. Actually, no, I meant what I said, the days get shorter in the summer and they get longer in the winter.
The first day of summer for those in the northern hemisphere is the summer solstice, which happens every year between June 20 and 22. On this day, the Earth’s 23.5 degree tilt is most tilted towards the Sun. Consequently we get the most sunlight, and we call that the longest day of the year. Therefore, if the first day of summer is the longest day of the year, then each subsequent day during the summer is getting shorter — the days get shorter in the summer.
This pattern progresses until the winter solstice, which happens, in the northern hemisphere between December 21-22, which is the shortest day of the year and the first day of winter. After winter begins, the days get longer until summer, and the pattern repeats.
I personally think we should just move to two seasons: summer and winter. Summer should begin on the vernal equinox, what we refer to as the first day of spring. For the first half of summer the days would get longer, and for the second half, the days would get shorter.
This would continue until we hit the first day of winter, which is currently the autumnal equinox, or the first day of fall. On the first day of (new) winter, the days would continue to get shorter, until current winter solstice, after which the days would get longer.