The Time Strip meter that you can stick to anything you want can show you how many days were you keeping it in the fridge. It is very convenient to know how "old" the food in order not to get sick from it. Earlier I was trying the food on my cat to know if it is still good to eat or not. I was giving a piece of it to my cat and if he eat it, it was ok. If not then I would through out the can. There are several types of Time Strip meters: they count days, weeks and month. You can also use the Time Strip meter with medicine, toothpaste and even your toothbrush.
It works very simply: there is some red fluid in it and it just slowly moves in a thin, capillary tube at a constant speed towards the end of it. It has a scale on it so you can see how many days, weeks, or months have past since you left it there. This tool is very useful for me and I hope that it would be useful for many other people too.