As I write this (June 14th) sunrise has occurred at the earliest clock time of the year – 5:05:33 a.m. in Concord, a tiny bit later where I am, an hour south. But it’s not the longest day of the year, meaning the most hours of daylight – that doesn’t happen until the solstice June 21.

Even though sunrise will be slightly later tomorrow than today, the hours of daylight will still increase because sunset will also be slightly later – and it will be a tiny bit more later than the sunrise. The latest sunset of the year happens June 26 this year.

Why the discrepancy? Because the Earth goes around the sun in an ellipse rather than a circle, so the length of the day (noon to noon) changes slightly over the course of the year. It would be too much of a pain to adjust the length of the day on our clocks 365 times each year so we average it out, which produces discrepancies between clock time and solar time.

As a result, the sunrise/sunset extremes – earliest or latest, depending on the season – happen about a week before (sunrise) and a week after (sunset) the solstices, which have the maximum and minimum of daylight hours.

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