WHAT IS........that jar symbol on my cosmetics?

So....I don't know how many of you have noticed this little symbol on your cosmetics but I'm going to explain what it means.
I am constantly being asked when do products 'go bad' and when products should be thrown out. Generally, its after a certain length of time which varies from product to product (Foundation can be 12 - 24 months and mascara 3 months) but this symbol is printed on the bottom of some bottles or pots.
The jar symbols means how many months the product is deemed 'safe' for. The number inside is the amount of months so the above product is 12 months. Most companies do print the PAO (Period After Opening) symbol, especially in Europe but I think it's optional in the states.