In Vito's office when Mike returns with Clemenza after the hospital thing, the clock on the mantle behind Sonny says 7:00. I'm assuming that AM since PM that time of the year would be in darkness. Is it AM the next day? That's seems a quick turn around for Mike since they had to dig some bone out of his jaw.
The novel said that doctors had to dig bone fragments out of Michael's
gums, not his jaw--implying a dental, not surgical, procedure. He might have remained in the hospital for another day or two. But, as the novel said, Sonny wanted him at the Mall right away. Sonny was probably concerned that Michael had shown his hand as a Corleone, and wouldn't be considered a "civilian" anymore.
Also, the hit on Bruno at 4 AM must have been quickly arranged since it appears to have happened only about 6-8 hours after the hospital thing.
They probably started planning a hit on the Tattaglias as soon as Vito was shot. I doubt they waited until after the second attempt on Vito's life.
