The “i” in the Hipmunk logo is capped with a triangle for a reason. Black triangles are the way to interact with one of Hipmunk’s coolest features: restricting the departure and arrival times of flights.
On the results page, you’ll find one black triangle at the earliest departure time. Just drag the slider inward to restrict the departure time (see images above). The same method works for the other black triangle (not shown above) for restricting the arrival time.
If you don’t feel like dragging the sliders yourself, choose one of the “filter by time” options, like No Morning Departures (see image above). The sliders will automatically move to cut off the flights you don’t want.