The TimeSlider

The TimeSlider shows you your current frame in the animation timeline,
and allows you to change the current frame by “moving through time”.

In the default UI layout, the TimeSlider is located on the left controller, on the upper side_ of the touchpad (HTC Vive) or thumb-stick (Oculus Rift)
and is indicated by the following icon:

The following video explains how to use the time slider:
https://www.youtube.com/watch?v=FsfReXmZ4hw

When you hold the controller button for the Time Slider, your Maya frame range will be displayed at the tip of your controller.

Move the controller from side to side to change your current frame.

When you hold down the controller trigger, the time change will be applied continuously, allowing smooth playback.
In this case, the distance how far you move the controller sideways from its original position (indicated by the blue arrow) will control the speed of plackback.

The Time Slider also indicates frames on which the currently selected object has keyframes by displaying a red key icon above the frame number:

The Time Slider will loop at the end of your Maya framerange, returning to the first frame in your frame range if you go beyond the last frame.