Waterfall plot X axis scale and timezone

[kasemir]

Assume I have a cavity amplitude waveform PV taken at 0.4µs per sample, 4096 elements. The waveform covers a time range of 4096*0.4=1638.4 µs and would like to show that as "0...1600 µs" or maybe "0...1.6 ms" on the X axis.

The waterfall plot, however, always shows the array index 0..4096 on the X axis:

Also, how can I change the "Time [UTC]" into local time?