With President Trump about to reach his 100th day in office (either April 29 or 30, depending on how you count), Washington and the news media are having a collective conniption fit. This arbitrary date on the calendar is supposed to somehow magically reveal everything that’s right and wrong with a new administration.

The first 100 days myth started during the remarkable whirlwind that was the start of President Franklin Roosevelt’s presidency. But using that unique time as the benchmark for measuring all succeeding administrations is severely flawed. Here’s why.