What Are the Odds of This Little Irony?

March 4 

United States Constitution declared in effect 1789, and Washington became first President, although not inaugurated until April 30.

Serfdom abolished in Russia 1861 by Alexander II.

From Anniversaries and Holidays: A Calendar of Days and How to Observe Them by Mary Emogene Hazeltine published by American Library Association (Chicago) in 1944.

The odds are 4 : 1461 (or 1 : 365.25 if you don't mind decimal places).