A container of leftovers is much more useful when you know what it contains and when it was cooked. The label does not need a special design or an app. A name and date are often enough to prevent the familiar question of whether that box arrived yesterday or several days ago.
Write the label while putting the food away. Waiting until later makes the date harder to remember, especially in a shared refrigerator. Use a method suitable for the container and cold conditions, such as removable kitchen labels or tape that will not damage the surface.
For a cooked meal, note when it was prepared. For an opened packaged food, the opening date may be useful alongside the package's own storage instructions. Transferring food to a fresh box does not reset its storage time.
USDA guidance generally gives refrigerated cooked leftovers three to four days when they have been handled safely. Freeze suitable portions sooner if you will not use them within that window. A label helps you follow the plan, but cannot make food safe after poor temperature handling.
Include details that affect how you will use the food. “Rice and beans, two portions” is more useful than “dinner.” In a shared home, an owner's name can prevent confusion. If allergen information is needed, keep the original packaging or an accurate ingredient record rather than relying on memory.
Do not make the label so complicated that you stop using it. A long form with boxes for every possible detail may be unnecessary for an ordinary leftover portion. Reserve extra information for meals where it actually helps.
Keep food that needs using toward the front, with labels facing outward. When adding a new portion, move older food where it can be seen rather than placing the new box in front of it automatically.
Before cooking another meal, scan the leftovers shelf. Decide what will be eaten, frozen or discarded, and update the label when appropriate. If you cannot establish how long food has been stored or whether it remained safely chilled, appearance and smell are not reliable substitutes for that information.
A consistent two-line label can do more for meal planning than a larger collection of containers. Its value comes from using it every time.