Had an idea for tupperware accessory. Please let me know if you've seen something similar, or if you particularly like the idea, etc.
Basically, it would involve having a day/month/year indicator built into the side or top of tupperware item. The indicator would be adjustable. Perhaps a rolling mechanism would be best.
This may insure that any items transferred to tupperware may carry a suitable use by date for the contents, to help make sure no food is wasted or consumed after food is risky to consume.
Another mechanism might involve attaching a (removable) use by tag to a container, possibly by suction cups, or replaceable and removable adhesives.