Every day is Sun day for the month of June, when the Sun is up for 15 hours plus a few minutes most days and darkness prevails, most days, for a few minutes less than 9 hours. The longest days of the year occur as Earth reaches the point in its orbit when the North Pole is tilted closest to the Sun, known as the summer solstice. This year, astronomers calculate that the solstice occurs on Saturday, June 20 at 5:44pm. According to my pencil on paper figuring from Starry Night* data, which is offered to a tenth of a second, day length at our location on Friday the 19this 3 seconds shorter than on the solstice and on the 20th day length is 2 seconds longer than on Sunday the 21st.
The chart, below, provides a picture, in numbers rounded to the minute, of markers in the progress of the day of the solstice. It is a useful guide until the end of June, given that day-to-day variations are just seconds.
Stephen Schneider, Professor of Astronomy, University of Massachusetts Amherst, adds to our understanding with this observation, “The sun’s angle relative to Earth’s equator changes so gradually close to the solstices that, without instruments, the shift is difficult to perceive for about 10 days. This is the origin of the word solstice, which means “solar standstill.”**