Today in History - December 23rd (O.S. December 12) 1777 - Alexander I of Russia

On December 23rd. 1777,  Alexander I of Russia was born in
Saint Petersburg (Russia).

Alexander I of Russia
Source picture: Wikipedia

His parents were Paul I of Russia and Sophie Dorothea of Württemberg.

Alexander I of Russia married Louise of Baden.
She took the name: Elizabeth Alexeievna.
They had 2 daughters.

Alexander I of Russia was well known for his wars against
Napoleon of France.

He died on December 1st. 1825 (O.S. = November 19th.)

What does O.S. & N.S. mean?

This means the use of the Julian calendar or the Gregorian Calendar.
Catholic Countries like, Spain, Poland, Portugal, Italy were the first
countries to change to the Gregorian Calendar (N.S.).
Other countries like Imperial Russia used the Julian Calendar (O.S).