Some dates produce men and moments that do not make sense until later. January 17 has a particular talent for this — for the warning given too soon to be heard, for the survival that arrives at too high a cost, for the birth of a mind that its own era could not fully contain. On January 17, 1706, Benjamin Franklin was born in Boston, the fifteenth of seventeen children of a candle and soap maker.

“Beware the Ides of March” is advice Rome gave the world, and the world has spent two thousand years testing whether it applies only to the original recipient. The evidence is mixed. March 15 has not always been violent. But it has, with some regularity, been the day someone discovers that the position they thought they held has already been vacated. On March 15, 44 BC, Gaius Julius Caesar arrived at the Theatre of Pompey for a meeting of the Senate and was stabbed twenty-three times by a group of senators who believed they were saving the republic.

There are days that do not begin wars. They announce them — standing at the edge of what has already been set in motion, making official what everyone has already understood. September 3 has had that function more than once: the date that formalizes an ending, ratifies a beginning, or simply states aloud what the situation already was. On September 3, 1783, American and British representatives signed the Treaty of Paris, ending the Revolutionary War.