On a PI Vision display you can control if the toolbar and/or timebar is shown with the URL parameters like HideTimebar. E.g.: https://webserver/PIVision/#/Displays/123?HideTimebar
However, these settings are inherited when another display is opened. So if you have a navigation link to another display where you don't have this set, the timebar is still hidden even if you did not explicitly hid the timebar.
It turns out that these switches allow a true/false boolean to override the inheritance, so if you need a timebar on a display, but navigate there from a display where the timebar is turned off, you need HideTimebar=false
Tested in PI Vision 2017R2. Original (but thus not entirely complete) documentation here: https://livelibrary.osisoft.com/LiveLibrary/content/en/vision-v2/GUID-C643F092-EB07-41EC-8DC8-5981BF2692F4