Track an opening date without inventing a universal lipstick expiry

Distinguish different kinds of dates

A printed expiry date, an after-opening period and a purchase date are different pieces of information. An unopened product bought long ago is not automatically equivalent to a newly opened one. Retain any date instructions instead of replacing them with an internet shelf-life chart.

Use the date planner as a reminder

Enter your real opening date and the interval stated by the manufacturer. The tool adds calendar months, clamping to the final day when a month is shorter. It does not examine the formulation, packaging condition or storage history and cannot certify that a cosmetic remains safe.

Take an earlier problem seriously

Unexpected changes in smell, texture or appearance deserve attention before any planned reminder date. Stop use when there is a concerning change and ask the manufacturer for guidance. Cosmetics that also make drug claims, such as sunscreen products, have additional labeling requirements; do not use an ordinary lipstick rule for those items.

Check the calendar rule with a real date example

As a calendar example, January 31, 2024 plus one month becomes February 29, 2024 because that target month has no thirty-first day. The same calculation in 2025 ends on February 28. This explains the tool’s date arithmetic; it does not assert that one month is a recommended lipstick interval. Enter a period from your own product instructions, retain any printed expiry date separately, and seek clarification from the manufacturer when those instructions are unclear.

Before you decide

• Record opening and purchase dates separately.
• Use an interval from the actual manufacturer.
• Do not treat the reminder as permission to ignore a product change.