Improve timer implementation to suit mobile browsers

[elenalape]

App relies on the browser being able to refresh content every one second.

This is unreliable in mobile browsers, unfortunately, because the window/tab is put to sleep when it's not active.

[meltq]

I would like to work on this issue

Proposal

Setting a new Date().getTime() for when you create a new timer, and get the time every second and subtract it from that, so even when the tab is inactive, the timer would go back to the right time when the tab does become active.