Fermat's Two Squares Theorem/Historical Note

Historical Note on Fermat's Two Squares Theorem
According to, on "Albert Girard" at Absolute Astronomy.com, Fermat's Two Squares Theorem was initially stated without proof by in $1632$.

announced its proof in a letter to dated December $25$, $1640$.

For this reason it is also sometimes referred to as Fermat's Christmas Theorem.

The first published proof was by after $7$ years of hard work.