A blood blister forms when skin and small blood vessels are damaged without breaking the skin. Trapped beneath the skin surface is some blood and skin fluid. Blood blisters are commonly caused by accidents in which the skin is pinched by a tool or a heavy weight, or they may occur from constant rubbing back and forth.
1 Sunshine hours in Chicago, Illinois range between 3:42 per day in December & 10:14 for each day in July. 2  The longest day of the year is 15:02 long and the shortest day is 8:57 long.  The longest day is 6:04 longer than the shortest day.
In the northern hemisphere, the longest day of the year is 21st June and the shortest day is 22nd December. The exact date can vary by a day or so. The same dates apply in the southern hemisphere, but with longest and shortest reversed. The summer solstice is the longest day of the year; the winter solstice is the shortest. In the northern hemisphere, the summer solstice is generally June 21, and the winter solstice is December 21. (Reverse these for the southern hemisphere.)