Below the visualization area, you find two sliders: The first controls the current time shown, while the second controls how quick the time advances in the visualization.
Directly after starting Via, the time slider does not show any indication of time. Only after loading some time-dependent data and visualizing it by adding corresponding layers will the slider display the range of time for which data is available. You can customize the shown range of time by using the menu
Time > Set Custom Time Range.... The Time menu also offers several commands to control which point in time is visualized.
When clicking on the displayed time or speed value, a small popup opens that allows to set the time or animation speed as a numerical value. Just type in the desired time or speed and press
Return to set the values. Instead of clicking on the shown values, corresponding menu entries with keyboard shortcuts are available in the Time menu:
Go to Time, or
Set Speed respectively.