Back in May 2011, I posted a general guideline (which can be found here) for safe make-up use.

Recently (thanks to beautyblogger Beautythesis), I’ve discovered a “cosmetics calculator”.
We all know (or should know) the hazards of using expired make-up (ie. skin irritations and infections, to name a few) so this calculator is a great tool that seems to be pretty accurate.

Cosmetics Calculator will help you determine your products expiration date by the batch code marked on your product.
A batch code is, basically, for the manufacturer to determine which batch the product was manufactured in.
Usually, you’ll be able to find the batch code near the bottom of the container.

To the left of Cosmetics Calculator screen, you will find a drop-down menu. Choose the cosmetics brand, enter the batch code and then, click calculate.

I hope you all find this helpful :)