Crack open your copy of the 2012 Farmers’ Almanac, and you’ll see that the earliest sunrise this year is listed for June 14 — at 5:13 a.m. at 45° North Latitude and 75° West Longitude.
Actually, the Sun is listed as rising at 5:13 a.m. every day from June 9th through the 21st, but it rises a few seconds earlier on the 14th than it does on the 13th or the 15th.
While everyone knows that the days are longer in the summer, many people are surprised to learn that the earliest sunrise of the year doesn’t occur on the longest day of the year. The summer solstice, which falls on June 20 this year, comes nearly a week after the earliest sunrise. By why?
The discrepancy is caused by the Earth’s elliptical orbit around the Sun. The Earth moves faster in its orbit during January (when we’re closest to the Sun) than in July, when we’re farthest away. Because of this motion, the Sun’s path through the sky, when charted on a day-by-day basis, appears to take a lopsided figure-8 pattern astronomers call an “analemma” (see below).
Because of this, the conventional wisdom that the Sun lies directly overhead at noon, splitting the day into two equal parts, is actually not true. The Sun can line up with the meridian as much as 15 minutes before or after noon. Anyone with a garden sundials is probably already aware of this discrepancy, known as “The Equation of Time.”
The Sun’s looping path also explains why the earliest sunrise of the year — and the latest sunset — do not exactly coincide with the summer solstice. Instead, the earliest sunrise occurs about a week before the solstice, while the latest sunset occurs about a week after the solstice.
A similar effect happens during the winter solstice, when the earliest sunset arrives about two weeks before the December solstice, and the latest sunrise occurs about two weeks afterward.
So, be sure to get up early on June 14th and greet the earliest sunrise of the year!