This extension will rescue your time by notifying you after a time limit while browsing time killing sites.
It can be a social platform (e,g, Facebook, Twitter), a news portal or a sports magazine. Whoever is killing your productivity, add them to watchlist. Then, when you are browsing any of these listed sites, timer will be activated in background.
After your time limit is over, it will display a system notification with a light, short alarm sound. That notification will also provide options to close all the tabs with that site or snooze for a few minutes. You can change the time limit and snooze time from settings page.
For details, check – http://ajaxray.github.io/session-timer/