Cosmetic dates: keep purchase, opening and label information separate
Build a simple record without confusing a batch code, purchase date or opening date with an expiry instruction.
Photograph before discarding the box
A product can arrive with useful information spread across its carton, base and container. Photograph the product name, printed date information and any opening-related instruction while they are readable. Keep the exact wording, rather than reducing every number to a single guessed expiry date.
Record the purchase date separately. Buying a product today does not establish when it was manufactured, and finding a code on the base does not tell you how to decode it. If the meaning is unclear, ask the manufacturer using a clear photograph.
Follow the product's own information
FDA guidance explains that cosmetic shelf life depends on the product and its storage and use. Its discussion also distinguishes ordinary cosmetics from products regulated as drugs in the United States. A universal replacement interval copied from a social post is not an adequate substitute for the relevant product instructions.
When the package gives a period after opening, preserve that information and record when you first opened the item. Keep a printed expiry date and an opening-period instruction as separate fields; do not overwrite one with the other.
Make the record easy to maintain
A small notebook entry can contain the full product name, variant, purchase date, opening date, label wording and where the reference photograph is stored. Put unopened backups in a separate place so that their status is obvious.
Review the record when reorganizing your shelf or packing a trip. If information has rubbed off, retrieve the photograph before guessing. The point is to retain the maker's guidance and your own history, not to invent a new guarantee of freshness.