Number of validations : 2274

Image challenge

That year in France, December 18th didn't exist, a result of the work of a mathematical scientist imposed on the world by a legal act.
1. What is the Latin name of this scientist?
2. What is the Latin name of this legal document?
The town where this scientist was born has a school named after him.
3. In which town did the current director previously work?
(Example: Maximus Decimus Extra Bellissima Berlin)