Where is the expiration date on a cardboard case of Diet Dr. Pepper?

We bought several cases of soda for our company kitchen from a local big box store. A coworker complained that the Diet Dr.Pepper tasted really off. Lo and behold on the bottom of each can is an expiration date and the soda in question had expired 4 months ago. The cardboard container is long gone so I have no way to check for a date. But we still had an intact case of Mountain Dew. The cans all had exp dates and they were all fresh, but the date was nowhere to be found on the cardboard container.

Is this normal? Am I going to have to open every case I buy from now on in order to prevent being sold an expired case?

It didn’t have an expiration date. It might have had a “best buy” date, but for most products, those are completely meaningless. Almost anything canned will stay good, for all practical purposes forever.

This isn’t entirely correct. Years ago I did consulting work for major soft drink bottlers doing transshipment tort investigations and I learned a few things.

Originally those dates (when a certain number was subtracted) along with the other codes on the bottom or side of the can indicated when and where the soft drink was produced. This made it feasible to determine if a bottler was selling product in another bottlers assigned district (many bottlers are not corporately owned but are franchises).
Some marketing genius thought up the “freshness code” thing to explain those dates to consumers.

However, some artificial sweeteners, Aspartame in particular, do deteriorate over time and affect the flavor of the beverage.

I don’t think this is necessarily true. I’ve certainly had canned beer that went bad.

Artificial sweeteners, at least some of them, definitely go bad/stale. And in my expeience the date on the can bottom gives you a good idea of when.

Truth. Diet Dr Pepper is sweetened with aspartame, which (as @pkbites noted) tends to stop tasting sweet after a year or so.

“Good” in the sense of not contaminated by bacteria, perhaps. But the flavor can certainly deteriorate over time. I personally poured a six-pack of way-past-the-date diet soda down the drain after tasting one can.

Not just artificial sweeteners. I don’t know about other soft drinks but Coca Cola has a shelf life of six to nine months, depending on how it’s stored. During the New Coke fiasco people were buying a year’s supply of the old formula before it ran out. I felt sorry for them.

My Ma still has 11 cans of New Joke sitting in her basement behind the bar. Back in the 80’s she bought a twelve pack of it. Drank one, said bleh, and the remainder have been sitting back there for over 30 years. I always kid with her that maybe it’s turned into a liquor.

I’m surprised it hasn’t eaten through the can by now.

I don’t have a case of anything here, but I’d be surprised if there wasn’t a date somewhere on the box. Probably stamped in small, black type on a black area. I’ve spent FAR too long finding dates on much smaller items, been SURE it wasn’t there, looked ONE MORE TIME and lo! there it was.

I don’t have Diet Dr Pepper handy but Diet Coke and Coke Zero both have clear exp dates on both ends of a 12pk.

And this is exactly why I rarely buy Diet Dr Pepper anymore. For whatever reason it seems way more susceptible to that skunky, ‘off’ taste than other diet sodas.

I buy for my department and their favorites are Diet Dr Pepper & Diet Mountain Dew. I get the 36-packs from a big-box store who shall remain nameless. These 36 packs do not seem to have dates on the outside. Or I am blind. Or the big box has a deal with the bottlers/canners to provide undated packages. I never see 36-packs in the supermarket.