Attack will be launched as follows:
Bombardment, attack to be made on Ford Island (in Pearl Harbor) at 7:30 a.m. ... Attack to be made on Clark Field (Philippines) at 10:40 a.m.
However, no one back home was eager to take Mitchell seriously. Because of a string of insubordination accusations, badass William Mitchell had developed a not-so-great reputation with the rest of the brass. In fact, the entire inspection tour had been a sort of forced vacation so that he couldn't make any waves back home. So it's easy to imagine all the masturbatory gestures his superiors made when Mitchell returned from his exile with a 324-page document about the martial danger some islands half a world away could pose.
As it turns out, Japan hit Pearl Harbor about 20 minutes after Mitchell said they would, then proceeded to Clark Field a few hours after. It even occurred on the same day of the week (Sunday) he had predicted. Of course, since he had died in 1936, the navy didn't really see the need to remind people they had been warned decades in advance. They did posthumously award him a Medal of Honor in 1946 for his efforts, so there's that.