I've noticed some Japanese food products (particularly snacks?) use some sort of non-standard code for their "best before" dates. Not all codes seem to be of the same type, so I suspect there may be more than one, maybe even vendor-specific?

An internet search for what I thought would be relevant terms (in both English and Japanese) turned out nothing more than general explanations of Japanese food labels, mostly addressed to tourists.

All three examples below are of Japanese products from different companies, recently bought in the US.

What do these codes mean? How do I know what dates they refer to?

Kingodo rice cracker: Z X 31

Sanko Seika sesame cracker: ZWR3

Amanoya kabuki age ichiban: E157

FWIW, I have no idea if this question is on topic here, but this is the closest I could guess to be applicable. If not, please accept my apologies and migrate to proper site.

  • 2
    For future reference - SE doesn't have a site for everything, so there isn't necessarily an appropriate site for each question :/
    – Mark Mayo
    Commented Nov 4, 2014 at 3:17
  • Oh, I know there isn't necessarily an appropriate site for every question, but there's definitely questions that are not appropriate for some sites, and some sites that are less tolerant of off-topic questions. :)
    – jja
    Commented Nov 4, 2014 at 4:40
  • The batch-code theory sounds promising. But... why print the code in the area clearly labeled "best before"? Because that at least is clearly not vendor-specific. Could it be to comply with some Japanese food-labeling regulation?
    – jja
    Commented Nov 4, 2014 at 4:42
  • It might be on topic on Japanese culture if that makes it to beta (it's currently in commitment phase). Commented Nov 21, 2014 at 12:00

1 Answer 1


Boring explanation: They're lot numbers (ロット番号), not expiration dates, referring to a batch of product made at the factory. So if you call them up and say "hey, there's wombats in my tofu", they can recall the lot in question.

As a consumer, you can't match a lot number to the expiration date (賞味期限), which you should find printed somewhere else on the packet. In your images I'd expect it to be printed in the same place, since all those spots are labeled "expiration date", but either the printer malfunctioned or it's printed elsewhere for some reason.

  • This is probably the right answer. I guess this is the closest I will get, although the best before date was definitely not printed anywhere else in the packages (I checked) and the fact that it was systematic, across brands, and so centered in that white area, makes me think a "printer error" is extremely unlikely. It seems more like they are intentionally using that space for the lot codes.
    – jja
    Commented Nov 5, 2014 at 21:17

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