Like the season? it was not invented. seasons occur naturally because of the tilt of the Earth towards the sun and things like that. All people had to do was come up with the name 'summer' and attach it to a time of year.
Summer x Summer was created on 2007-03-11.
How I Spent My Summer Vacation was created in 2000.
"Ika Summer" was created in 2012 by the Japanese game development company, Idea Factory.
It's a Summer Vacation Everyday was created on 1994-06-11.
How I Survived My Summer Vacation was created on 2000-08-01.
Summer x Summer was created on 2007-03-11.
That Summer was created in 1996-10.
Summer in Bethlehem was created in 1998.
Summer's Desire was created in 2009.
The Comrades of Summer was created in 1992.
Dry Summer was created in 1964.
The Summer Obsession was created in 2004.
The World That Summer was created in 1986.
Come Summer was created in 1969.
The Summer Garden was created in 2005.
Mad Summer was created in 2004.
Bicycles Are for the Summer was created in 1984.