Maybe you’ve come across a sake bottle with a neck label or sticker proclaiming “28BY” or “R1BY”. But what does it mean?

BY=Brewery Year

BY stands for Brewery Year. A brewery year runs from July 1 to June 30 of the following calendar year.

The number refers to the Japanese era system, which counts the years of an Emperor’s reign. The period from January 8, 1989 to April 30, 2019 is known as the Heisei Era [㍻]. When Crown Prince Naruhito became the new Emperor of Japan in May 2019, a new era started. The current era is called Reiwa [㋿]. The era names can we written with the characters shown here, but are often abbreviated as simply H or R respectively. But as most sake isn’t stored over many years, there’s no real risk of confusion.

Japanese era conversion table

H27 — 2015
H28 — 2016
H29 — 2017
H30 — 2018
H31 — 2019 (only until April 30!)

R1 — 2019 (from May 1)
R2 — 2020
R3 — 2021
R4 — 2022
etc.

A small but increasing number of breweries don’t use the era system but write the Gregorian year instead, i.e. 2018BY.

Brewery year vs. release date

So a sake brewed between July 2019 and June 2020 would be labelled 令和1BY, R1 BY or simply 1BY.

Note that this is not compulsory; breweries only have to print the date when the bottles left the brewery and were released into the market. For example, a sake brewed in H30 (=2018) could have been stored at the brewery for a few years, before being released for sale and thus have a much more recent release date printed on the label.

In contrast to the brewery year, the release date is always printed following the Gregorian calendar and in ISO-standard format (Year.Month.Day), e.g. 19.11 for November of 2019.