Read the number on your own pack
Find an open-jar icon on the container, carton or accompanying information. The number and M indicate months after opening. For example, 6M, 12M and 24M mean six, twelve and twenty-four months respectively.
A 3M label means three months; it does not establish a rule that all products of a particular type have that period. Do not transfer the label from one moisturiser, mascara or fragrance to another, even within the same brand.
Keep the symbol in your label photo. The plain number 12 elsewhere on a package might be a shade, size or product reference instead.
Count from first opening
Write down the date when you first open the product for use. Buying it, receiving it or looking up its batch number does not start this clock if it remains unopened.
For a hypothetical product opened on 10 April 2026, 6M gives a six-month planning date of 10 October 2026; 12M gives 10 April 2027; 24M gives 10 April 2028. These examples explain calendar arithmetic, not a guaranteed usable lifetime.
Closing the lid, moving the product into another container or stopping use for a few weeks does not restart the recorded period. If the brand gives more specific opening or use instructions, follow those.
Keep PAO and expiry dates together
A labelled expiry date and PAO answer different questions. Record both if both are present. A later PAO calculation does not extend an earlier labelled deadline.
Use the shelf-life worked example to compare known limits. Do not fill in an unknown unopened lifetime using a general rule, and do not assume a batch checker can supply the opening date.
What PAO cannot measure
The symbol communicates a use period; it is not a test of an individual bottle. It cannot tell whether a container was previously opened, exposed to unsuitable conditions or contaminated.
Keep applicators and containers clean and follow the storage instructions. If the product changes or there is a problem during use, do not rely on the months remaining as reassurance. Normal appearance also cannot validate an uncertain history.
If the symbol or opening date is missing
Inspect the outer carton and instructions first. Some products have different labelling arrangements or do not carry PAO. Absence of the icon is not evidence that the product lasts indefinitely.
For an unknown opening date, write “unknown” rather than restarting the clock now. The brand enquiry template lets you ask about the exact product and provide its label details. If you are trying to identify manufacture instead, use the batch-code basics guide.
Sources and scope
Cosmetics Europe: Understanding the label
European industry guidance on batch identification, label dates and the open-jar symbol; it does not publish decoding rules.
FDA: Shelf Life and Expiration Dating of Cosmetics
U.S. guidance on product deterioration, storage and manufacturer responsibility; it does not validate this checker or any individual product.
Sources support the labelling and shelf-life context. The inspection steps and enquiry template are practical guidance from CosmeticBatchTool, not manufacturer confirmation of an individual item.