@idefix37 Thanks. The inconspicuous "Speed Button" (a grey letter G) did the trick. I was looking for a way to turn it on. The App has a slider toggle, why a letter on the desktop? I used to be a toggle, right?

@idefix37 I have only used it on the desktop until yesterday when I tried it in the app.
I have used the desktop version successfully many times over the years and never had this trouble before.
Neither the desktop nor the iPhone app work for me.
So I can slide the start time back and forth on the timeline but it doesn't show the end time/duration and the weather doesn't change as I hover though the timeline.

@jmh2002 It doesn't let me choose the departure time/day, nor does the weather change as a drag through the days.