@geftactics thanks! but why is this part needed?

function hideTime() {

     $all('.clock button').forEach(item => {
         let time = item.querySelector('time')
         time.innerText = ":"
     })
 }

When the app window is hidden, we remove the current time from the clocks with this function.

This prevents the old time from being shown for a few milliseconds next time the app window is opened, so a cleaner redraw experience.

But with next tick all clocks in background recalculated from fn runClock()

Yes, but this doesn’t happen instantly… (it doesn’t look like tick happens when window is hidden?)

if I hide that app window at 22:49, then later open it at 23:00… I will see the 22:49 on screen for a split second before the tick happens and clocks are updated (you have to look hard for it, but it was bugging me each time I opened the app!)

This change just hides the old time to make this glitch less apparent when opening the window.

I could record a video and slow the speed down to show the issue if you are not seeing it