I find that I use these cartons of broth a lot in my cooking but I don't always use the whole thing. They obviously have a printed expiry date right on them but that is only good as long as the carton hasn't been opened. Once it is open, you are required to use it within 2 weeks. Great - I can throw it in the fridge and pull it out another night. Of course remembering when you opened it when you're in the midst of another dinner whirlwind is a challenge in itself.
So now I simply write the date that it is good until using a black Sharpie right on the package. I do this for other items that must be used within a certain number of days from opening. No more guessing, the number is right there in front of me.
I find that writing the date it is good until works better for me than writing the date that I opened it. This means only doing the math one time instead of every time I might want to use a bit.
I have a lot less waste this way and will even find myself coming up with meal ideas that incorporate the ingredient if I see it in the fridge with a short expiry date on it. Give it a try in your home. Let me know how it worked!