Today is the Ides of March. Here is what Plutarch wrote in his Life of Caesar:

The following story, too, is told by many. A certain seer warned Caesar to be on his guard against a great peril on the day of the month of March which the Romans call the Ides; and when the day had come and Caesar was on his way to the senate-house, he greeted the seer with a jest and said: "Well, the Ides of March are come," and the seer said to him softly: "Ay, they are come, but they are not gone." Moreover, on the day before, when Marcus Lepidus was entertaining him at supper, Caesar chanced to be signing letters, as his custom was, while reclining at table, and the discourse turned suddenly upon the question what sort of death was the best; before any one could answer Caesar cried out: "That which is unexpected."

At all events, when day came, she begged Caesar, if it was possible, not to go out, but to postpone the meeting of the senate; if, however, he had no concern at all for her (his wife’s) dreams, she besought him to inquire by other modes of divination and by sacrifices concerning the future. And Caesar also, as it would appear, was in some suspicion and fear. For never before had he perceived in Calpurnia any womanish superstition, but now he saw that she was in great distress. And when the seers also, after many sacrifices, told him that the omens were unfavourable, he resolved to send Antony and dismiss the senate.

But at this juncture Decimus Brutus, surnamed Albinus, who was so trusted by Caesar that he was entered in his will as his second heir, but was partner in the conspiracy of the other Brutus and Cassius, fearing that if Caesar should elude that day, their undertaking would become known, ridiculed the seers and chided Caesar for laying himself open to malicious charges on the part of the senators, who would think themselves mocked at.