The Romans didn't number the days of the month sequentially. Without going into a lengthy, and potentially dull, explanation the Ides were determined by the full moon. And the Ides were sacred to Jupiter, the supreme deity of the Romans.
Julius Caesar was assassinated on the Ides of March, March 15th. This being March 15th I thought I'd highlight my Caesar inspired bracelet.
"Alea Jacta Est" ("the die is cast)." This quote was attributed to Caesar as he led his army across the River Rubicon into Italy. He knew that by doing this he had to either win or die. There was no turning back.
The phrase is still used to mean that events have passed to the point of no return and events will proceed in an irreversible way.