Here's a neat little invention that will time anything, but is being touted to parents in particular for use on baby's food: The DaysAgo Digital Day Counter is a round little timer with your choice of either a magnet or a suction cup on the back. Stick one on top of that jar of strained carrots before you toss it in the fridge, and when you find it hiding behind the orange juice later in the week there will be no guessing about how long it's been there.

If you can't keep track of these things and don't have a single Sharpie in the house (I used to just write the date on the label, but I'm a Luddite), two-packs of the DaysAgo timers can be had for $10 apiece.