Confusing Use Of Numbers: Best-Before Dates

My wife was driving me and our children to Collingwood yesterday. I was hungry, and found a power bar in the glove box, with a best-before date of


Yesterday was 20 February 2012, and my question is: had the best-before date passed yet?

In Europe, it is typical to write dates in the form “day/month/year,” so if this were Europe, then the best-before date would have passed, and I perhaps ought not to eat the bar. (Although the best-before date would not have passed by too much, and usually the time at which the food is spoiled is beyond the best-before date, so perhaps eating it would be OK.)

In North America, the year is usually last, but the day and month could be in either order. But there are six possible permutations of the six data, so although only two of the permutations are in common use (“year/month/day” is also used, but less commonly), there is still room for confusion. For something as important as best-before dates, shouldn’t we have an unambiguous usage convention? Clarity is courtesy, but when it comes to best-before dates, clarity could also save someone from illness.

But it is difficult to reach consensus on conventions, particularly in this case with products being produced around the world. So here is my proposal for ensuring that best-before dates will never be misinterpreted:

1. Always write all four digits of the year.
2. Always use a day that is at least 13.

Then it doesn’t matter which permutation is used. The dates 13/02/2012, 02/13/2012, 2012/13/02, etc., can only be interpreted in one way. And if a packaged food is good for a year or more, then altering the day by a few to ensure that it is at least 13 will cause no problems. In my situation, this would have saved me wondering whether the best-before date was 9 February or 2 September, or even some time in 2009 (2002 seemed unlikely).

If the food product is only good for a few days after packaging (which is the case for meats, bread, and some other foods), then it is unlikely that it will travel far, and the word for the month could be safely used.


About Santo D'Agostino

I have taught mathematics and physics since the mid 1980s. I have also been a textbook writer/editor since then. Currently I am working independently on a number of writing and education projects while teaching physics at my local university. I love math and physics, and love teaching and writing about them. My blog also discusses education, science, environment, etc. Further resources, and online tutoring, can be found at my other site
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5 Responses to Confusing Use Of Numbers: Best-Before Dates

  1. In the Air Force we were instructed to use the following format: 21 Feb 2012. I don’t know how anybody can stand using any of the ambiguous systems

  2. Joe says:

    Some manufacturers stamp numbers on their packages. I have a bottle of mustard that has 1214 15:31 time-stamped on the side of the bottle and AMPAK 125MLU 21 engraved on the bottom. It probably has relevance to the maker, but what the heck do these mean to a consumer?

    Did you eat the bar?

    • Well, I was hoping that nobody would ask me if I ate the bar! I did, and I had a stomach ache later, which persisted into the next day, so maybe it was not so wise to eat it. But who knows, maybe something else caused the stomach problem.

      I think the numbers stamped on products are probably useful in case of recalls … they can identify which products were made on which day, and so on.

  3. khhsocratica says:

    If only we could reform the dating conventions! We make educational videos, and we handle a lot of files (audio, video, etc.) that need to be found quickly and put together properly (one day’s audio needs to be synced with that day’s video, and the shot notes in a google doc need to be quickly found and used)…From the start, we used the format 4-digit year.2-digit month.2-digit day (for example, files from today are 2015.06.10) and what an unexpected blessing that has been. We do work with people all over the world, and thankfully it has never caused any confusion.

  4. Vincent Lidou says:

    why not make manufacturers write somewhere on the box the date format they will be using – something like yy-mm-dd ?

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