March 23, 332 (traditional date): Gregory the Illuminator, who converted a nation before Constantine even embraced Christianity, dies. A missionary to his homeland of Armenia, he converted King Tiridates, and much of the kingdom followed suit. Soon Christianity was established as the national religion, with Gregory as its bishop (see issue 57: Conversion of Rome).

March 23, 1540: Waltham Abbey in Essex becomes the last monastery in England to transfer its allegiance from the Catholic Church to the ...