How to read the date code on food packaging

Some packages print a plain date: a day, a month, a year, maybe the words "best before" right in front of it. Others print something that does not look like a date at all — a short run of digits, or a letter and a number mixed together, often stamped in ink that looks different from the rest of the label. That second kind is usually not written for you. It is a production code, and reading it as an expiry date is where a lot of the confusion starts.

Two different jobs, printed in two different ways

A best-before or use-by date answers one question: how long is this good for. A lot code, batch code, or plant code answers a completely different one: which production run made this specific package. Manufacturers need that second answer for reasons that have nothing to do with your kitchen — if a problem turns up in one batch, the code is how they trace it back to a specific line, shift, and day of production, and pull only that batch rather than everything sold under the same product name. It is a recall tool, not a freshness tool, and it gets printed whether or not a calendar date appears anywhere near it.

The two often sit right next to each other, stamped by the same machine in the same pass, which is exactly why they get read as one thing. A carton might carry "BEST BEFORE 08 2027" in clear print and, underneath it, a second line like "L4 21:07 B142" that means something specific to the plant that made it and nothing at all to the person holding it.

The Julian code, the one that trips people up most

The classic confusing case is a short block of digits with no slashes, no month name, and no obvious calendar shape — something like 3142 or 23142, stamped near the seam of a can or the base of a bottle. This is usually a Julian date code: not a calendar date but a day count. A four-digit version typically reads as one digit for the year plus three digits for the day of that year, so 3142 means the 142nd day of a year ending in 3 — roughly late May. A five-digit version adds a second year digit for less ambiguity. It is a genuinely useful format for a factory tracking millions of cans, and a genuinely opaque one for anyone who has not been told the rule.

There is no single key that unlocks every Julian code — some manufacturers count from January 1st, some order the year and day digits differently, and store-brand products packed by different co-packers do not always agree with each other. What is worth knowing is simply that a plain string of digits with no obvious date shape is very likely this kind of code, not a warning that something is unusually close to turning.

What actually differs by country, and what does not

Where a genuine calendar date does appear, the order of day, month, and year is not universal either, which causes its own confusion. Month-day-year is common in the US; day-month-year is standard across most of Europe and much of Asia; year-month-day is standard in Japan and mainland China, and is also the order used in international ISO date formats. A date printed as 03-04-25 could mean three different days depending on which convention the package follows — one more reason a genuinely unclear date deserves a second look rather than a fast guess, especially on imported goods where the printing convention may not match the one you are used to reading.

When the code genuinely will not resolve into an answer

• Look for a plain-language word nearby first. "Best By," "Use By," "EXP," "BB," or the local-language equivalent almost always marks the actual consumer-facing date, even in a row of other stamped digits. That is the one to read; everything else on the same line is usually for the plant.
• A pure digit string with no such word attached is almost always a production or lot code, not a date. Treat it as identifying the package, not the timeline.
• If it genuinely will not resolve, the manufacturer's own contact information — printed on most packaging — is the accurate source, not a guess. This matters most for a recall notice, which references the exact code rather than the product name.
• Absent a clear date, fall back on the general storage guidance for that category of food rather than the mystery code. A sealed can of tomatoes or beans that shows no sign of bulging, rusting or leaking, stored somewhere cool and dry, behaves the same way whether or not you can decode the stamp on the bottom.

None of this requires memorising a factory's internal system. It requires knowing which printed word is actually written for you — and treating the rest of what is stamped on the package as exactly what it is: information for the people who made it, not a countdown for the people about to eat it.

Munch does not ask you to decode anything printed on a package in the first place. You log what you bought and when, and the app tracks its own dates from there — a separate, shorter countdown that starts the day you mark something opened, shared in real time with everyone in the household — so the number that matters is the one you actually entered, not one stamped in a factory's own shorthand.