I'm working on updating the Pavuk application for Q research so that we can search for posts with given days or times. It enables you to enter any combination of the criteria for a query. The ClockFags look at x minutes after the hour.
In this prototype for discussion, we're simply entering 15 to find all posts that were 15 minutes after the hour.
If we wish to find everything that happened at 4:15PM, we'd put 16 into the hours box.