The Ides of March
Today is the “Ides of March,” the day that commemorates the death of Julius Caesar. In March, the “Ides” always falls on the 15th, but that’s not true of other months. William Browning explains:
The Roman calendar had weird ways to determine times of the month. The Ides of March doesn't necessarily refer to a holiday or festival on the Roman calendar but instead talks about how the Romans told time in the year....
The calendar organized months around three days -- Kalends, Nones and Ides. Kalends noted the first of the month, so in modern terms the Kalends of June would be June 1. Nones served as the seventh day in March, May, July and October; it was the fifth in every other month. Ides were the middle of the month -- they were the 15th of March, May, July and October but the 13th in others.
Days were noted by counting backwards from the upcoming monthly marker. For instance, Oct. 10 would be designated the "V Ides" or five days before the Ides of October. This method of dating lasted well into Medieval times before it was replaced with the Gregorian calendar used today.
The plot against Caesar was a reaction to his efforts to increase his power and become “dictator for life.” According to National Geographic:
The Romans had no love for kings. According to legend, they expelled their last one in 509 B.C. While Caesar had made pointed and public displays of turning down offers of kingship, he showed no reluctance to accept the office of "dictator for life" in February 44 B.C. According to Osgood, this action may have sealed his fate in the minds of his enemies. "We can see [now] that that was enough to get him killed," Osgood said.
Caesar had pushed the envelope for some time before his death. "Caesar was the first living Roman ever to appear on the coinage," Osgood said. Normally, the honor was reserved for deities. He notes that some historians suspect that Caesar might have been attempting to establish a cult in his honor in a move towards deification.
Caesar’s assassination did little more than delay the process, for his heir Augustus became Rome’s first emperor fifteen years later.