- Memorial Day to Labor Day
- Summer Solstice to Autumnal Equinox
- First day of June to last day of August ("meteorological summer")
- Last day of school to the first day of school
Since school is the one that has the biggest direct impact on the most lives, let's count it double, using both a random college and a random high school.
For the Memorial Day to Labor Day one, there are almost always exactly 14 weeks of summer. (One out of every seven years it's 15 weeks, but let's ignore that.) This year is a pretty average one in terms of how early/late each holiday can fall, so let's use it. There are 98 days of summer from May 28 through September 3rd, making Midsummer Day today, July 16th.
This year, the summer solstice was June 21st and the Autumnal Equinox will be September 23rd. That makes a 94-day summer, with Midsummer Day on August 7th.
Meteorological summer has 92 days. The midpoint always falls on July 17th.
For our college example, let's use Penn. Penn's new schedule seems to have finals ending on the second Tuesday in May, and fall convocation on the day after Labor Day. This is either 112 or 119 days. Based on all of the possible configurations, it turns out that Penn's Midsummer Day falls, on average, on July 8th.
I can't figure out the Philadelphia School district's rules for calendar making, so I'm just going to ballpark it. The mode of the September starting date for students in 2004-2007 is September 7th, and the mode of the June ending date for students in 2005-2008 is June 19. This gives an 80 day summer (poor kids), and Midsummer Day is July 29th.
So what's the conclusion? Well, first of all, there's a brief period, from June 21st until July 8th, when everyone agrees that it's the first half of the summer. And there's a similar period, from August 7th until around the start of September (though I didn't take into account the many schools who get going in late August) when everyone agrees that it's the second half of the summer. In between fall all of the Midsummer Days. The mean midsummer day is July 22nd. And the median is tomorrow.
The majority opinion, then, states today for the last time this summer that we've got more summer ahead of us than behind us. I don't know about you, but to me, that's reason to celebrate. Happy Last Day Of The First Half Of The Summer According To Majority Opinion! (And happy birthday, Jeffy! And happy birthday, Val!)