The media seem to be overly concerned with the story of President Trump’s first 100 days in office, as if 100 days made more sense than 105 days (15 weeks) or 91 days (one quarter/ three months). However, it just does not matter. There is no historical evidence that events in the early days of a president’s term have anything to do with how history views overall presidential performance.
Take Abraham Lincoln, for example. Fewer than two month after taking office, Fort Sumter had been fired on and the country was embroiled in the Civil War, about the biggest disaster of any presidency. Or consider John F. Kennedy. Before his first 100 days were over, he was responsible for the catastrophe at the Bay of Pigs.
In spite of these first 100 day failures, both of these men are generally viewed as better than average presidents.