^^^^
Don't know if you're joking, but if you seriously don't know:
The midpoint of any month is the "ides" of that month.
Don't know how they figure it for February.
The fifteenth is the "ides" of most months.
Some fortuneteller warned Julius Caesar to "beware the Ides of March".
And sure enough that was the day that the Roman senators all carried out their plot, and stabbed Caesar to death. Each one plunged a dagger into him.
And its all retold in the Shakespeare tragedy "Julius Caesar".
As Caesar died he saw that his erstwhile friend, Brutus, was among the stabbers, and he famously said "et tu Brute'" ( and you too Brutus????), as Caesar breathed his last breath.