Meteorologists say summer starts on June 1. Many others hold out for the day of the solstice, June 21 this year. Not very many argue for May 11, but they, too, could cite reasons.

This year, Sunday is not only May 11, but also Mother’s Day. That, however, may be beside the point. What distinguishes Sunday is that it starts a period of about 12 weeks when it stays light the longest — a time of early sunrise and late sunsets when daylight is as close to endless as it gets in Washington.

Those long days do not begin with June 21, the day of the solstice, the longest day of the year. By the time June 21 arrives, half of the year’s longest days, the days on which darkness is least likely to curtail outdoor activities, have passed.

On Sunday, the interval between sunrise and sunset in Washington is about 14 hours and 10 minutes. At least that much daylight is available on each of the 83 days from Sunday to the first day of August, both days included. The period is one day short of 12 weeks.