It's Mid Summer!

Portrayal of a Midsummer's dance in Scandinavia.

June 21, you're thinking?

Nope, June 24. St. John The Baptist's Day on the Christian calendar. 

Midsummer's Eve is June 23.

And yes, they were big deals.

Big Christian deals, it should be noted, but they did have a tenancy in some places to get out of hand.  Indeed, Midsummer's Eve was made that as cleric's in England felt that people were letting the revelry get out of hand on the saint's day and it was an effort to put the festivities on another day.

Traditionally the day was celebrated with feasting and parties, but also religious observances.  The more Catholic the country, the more likely the religious significance of the day is likely to be retained, but even in Protestant countries the significance was often not lost and all through Northern Europe some observance of Midsummer tends to be retained.

French peasants celebrating St. John the Baptist's day.

Well what about Shakespeare's play?  Well, it's simply set on the day.

And "Midsummer", what's up with that?  Summer starts on June 21, right?

Well, not really. Most people don't figure summer that way anywhere.  In the US Memorial Day usually is regarded as kicking off summer.  In more agrarian times, summer was calculated to start about the time planting really got rolling,. and run to the harvest.  This was, mid summer.

And in a lot of ways, it still is.