The time strip is an innovative timer-on-a-sticker. The timing countdown starts on a pretedermined schedule using a liquid membrane that allows a chemical to travel down a channel when you press an embedded button.
Anyone trying to figure out if their milk is too old, or more importantly, if their vaccine vials have been exposed for too long should look into adding these into their shopping list ($14.50 for a 50 pack). They even have an accidental freezing event indicator. The British company, is obviously doing their homework.