I'm paranoid about food safety. So I'm always throwing things out when in any doubt. My husband and I debate who opened what and when.
Hopefully we'll have fewer of those conversations now.
I simply put a Sharpie permanent marker in the magnetic holder on the refrigerator.
When anyone opens a new jar of something they are supposed to write the date on the lid.
You can even use the permanent marker to write the date on glass dishes with leftovers. The marker comes off with fingernail polish remover.
If you want to high tech you can invest in these digital timers.
The DaysAgo Digital Day Counter counts down days until the food expires based on how many days you set. It has a magnetic backing and attaches to a variety of things.
The Bean Tag timer will actually beep to remind you before the food expires. Perhaps I should get some of those to attach to bills.