"I know it's your birthday"

Riddle:

 

He had daydreams that changed the world. The solution to this integral gives his birthday.

Whose birthday is it?

 

 

This is a riddle for the Brain Food : Riddles group (Please read the Rules of the group). If you think you have the answer to the riddle send me a message, please don't reveal all in a comment.

You are also welcome to leave comments.

 

 

 

Done