BY: Finding the Brewing Year Hiding on a Sake Label

Pick up a bottle of sake and you may find two date-like markings on the label. One is a month and year. The other, if it appears at all, is a short code beginning with the letters BY. They look similar enough that drinkers often assume they mean the same thing, or that one is simply a more precise version of the other. They are not. They answer different questions, and knowing which is which changes how you read a bottle.

This is not a wine label. Sake does not carry a vintage in the way a Burgundy or a Barolo does. But there is a brewing year, and on some bottles it is printed plainly for anyone who knows where to look.

What BY actually means

BY stands for brewery year. When you see BY2019 on a label, it means the sake was brewed in the 2019 brewing year, which runs on the brewing calendar rather than the Gregorian calendar. That definition comes from the Japan Sake and Shochu Makers Association’s own label-reading guidance and is repeated in export-facing label guides: BY2019 means the sake was brewed in the 2019 brewing year, which runs on the brewing calendar rather than the calendar year.

That is the whole of what the label tells you. It does not tell you the sake is better, older in a meaningful sensory sense, or more valuable. It tells you which brewing season the liquid came out of. Everything else — how it was stored, how long it sat, whether it was blended — is a separate question.

The date you are most likely to find

The date item most commonly found on a sake label is 製造年月, usually translated as date of manufacture or date of production. The Japan Sake and Shochu Makers Association describes it plainly: the date of production indicates when the sake was bottled, regardless of the brew date. A separate export-facing guide puts it in slightly different words: the manufacturing date required on labels describes when the brewery decides to release the sake from the brewery.

Both descriptions point to the same practical reality. The date you are most likely to find is a release date, not a brewing date. It marks the moment the bottle left the brewery’s control. It does not mark the moment the sake was made.

There is a small-container exception worth knowing. For containers of 300 ml or less, a code can replace the date. If you are holding a one-cup or a small format bottle and cannot find a month and year, that is why.

Why the two dates can be years apart

Sake is not typically brewed and shipped in the same week. The Japan Sake and Shochu Makers Association notes that most sake is shipped after almost one year of maturing, and some sakes are aged beyond that, sometimes for years. A bottle can therefore carry a recent release date and a brewing year from several seasons earlier. The gap is the time the sake spent under the brewery’s care — or, depending on the bottle, under someone else’s.

This is where the two markings start to be useful together. A recent release date tells you the bottle has not been sitting in a warehouse for a decade. A brewing year tells you when the liquid was actually made. Neither one alone gives you the full picture.

Where BY sits in the labeling hierarchy

Here is the part that trips people up. BY is not a required label item. It is optional. Its absence is not a red flag, and its presence is not a legal requirement being met — it is a choice the brewery made.

That choice is meaningful. A brewery that prints BY on a bottle is signaling that it expects the drinker to care about when the sake was brewed. That is most common on intentionally aged sake. The export-facing label guide is direct about this: for intentionally aged sake you will find the brewery year on the label, with BY2019 given as an example of brewery year 2019.

There is a related optional item worth knowing: storage years. Sake stored for more than one year can be labeled with the number of years rounded down to the nearest year. When different-aged sake is blended, the age of the youngest sake is listed. So if you see a storage-age figure, it is a floor, not an average.

The Japan Sake and Shochu Makers Association defines jukusei-shu — aged sake — as sake professionally aged for more than two years after brewing. That is a useful threshold to keep in mind when you are trying to decide whether a bottle is being sold as a fresh drink or as an aged one.

A note on the 2023 labeling change

The rules around the date of manufacture changed. According to a regulatory summary of the National Tax Agency’s 2022 notice, the indication of year and month of manufacture was changed from a required labeling item to a voluntary labeling item, in line with Codex standards and food labeling standards, applicable from January 1, 2023. The same revision allowed date indication in accordance with product characteristics — date of shipment, for example — rather than a single fixed format.

This is worth stating carefully, because it is easy to overread. The change was a change in status, not a removal. It does not mean the date disappeared from labels, and it does not mean you should stop looking for it. It means the date is now something a brewery chooses to print rather than something the law compels. In practice, most bottles you pick up will still carry a date. But the fact that it is now voluntary is one more reason to read what is actually on the bottle rather than assume a format.

How to read a bottle in practice

Here is a routine that works whether you read Japanese or not.

First, find the release date. Look for 製造年月 followed by a number. In the format used by many breweries, 製造年月 24.6 means June 2024. This is the item you can most reliably expect to find.

Second, look for BY or storage-age wording. If BY appears, note the year. If a storage-age figure appears, note that too. If neither appears, that is normal — it just means the brewery did not choose to print it.

Third, decide what kind of purchase you are making. A bottle with a recent release date and no brewing-year marking is most likely a fresh-drinking purchase. A bottle with a visible BY several years earlier than its release date is being sold, at least in part, on its age. Those are different decisions.

Fourth, if you cannot read the label, photograph it. Take a clear photo of both the front and back label. Ask a retailer to identify which number is the release date and which, if any, is the brewing year. Guessing from a two-digit number alone is the main way to misread a bottle. A number that looks like a year might be a brewing year, a release year, a rice-polishing ratio, or something else entirely.

What BY does not tell you

It is worth being explicit about the limits, because the temptation to treat BY as a quality score is strong.

A visible BY does not mean the sake is better than one without it. It does not guarantee a particular flavor, aroma, or texture. It does not tell you how the bottle was stored after it left the brewery. And it does not tell you whether the sake was blended with other ages — if it was, the storage-age figure, when present, reflects the youngest component.

What it does tell you is that the brewery expects you to care about when the sake was made. That is a signal of intent. It is not a guarantee of outcome.

Why this matters for drinkers outside Japan

If you are buying sake in a market where you cannot read the label and cannot visit the brewery, the label is your only source of production context. The Japan Sake and Shochu Makers Association notes that sake labels include information on how the sake is made, the sake type, and particular ingredients, and that this information helps consumers understand the flavors, aromas, and textures to expect. The date markings are part of that.

Knowing the difference between a release date and a brewing year does not make you an expert. It makes you a better reader of the one document you actually have in front of you. That is the whole point.

Frequently asked questions

Is BY the same as a vintage?
No. A wine vintage refers to the year the grapes were harvested. BY refers to the brewing year the sake was made in, which runs on the brewing calendar rather than the Gregorian calendar. The two are not equivalent.

Why does my bottle not have a BY?
Because BY is optional. Its absence is not a problem. It simply means the brewery did not choose to print it.

Does a recent release date mean the sake is fresh?
Not necessarily. The release date marks when the sake left the brewery, not when it was brewed. A bottle can carry a recent release date and a brewing year from several seasons earlier.

What if I see a number like 24.6 on the label?
That is likely a release date in year-month format — June 2024 in this example. It is not a brewing year.

Can I rely on the date of manufacture to tell me how old the sake is?
No. It tells you when the sake was released from the brewery. The brewing year, when printed, tells you when it was made. Those can be different.

What should I do if I cannot read the label at all?
Photograph both sides and ask a retailer to identify the markings. Do not guess from a two-digit number alone.