Beer date codes can be harder to interpret than ordinary expiration dates. They aren’t standardized: some breweries print a “best by” date, others use a “born on” date, and some include both.

A “best by” date estimates when a beer may begin to lose flavor; it generally isn’t the same as a safety expiration date. A “born on” date tells you when the beer was packaged. For the freshest taste, look for the most recent packaging date. It can also help if you’re aging beer, since different styles change over time in different ways.

Date formats vary

In the U.S., dates may appear as month/day/year, such as 01/12/2026 for January 12. Some breweries spell out the month in a code like JAN1226. Elsewhere, day/month/year is common, so the same numbers could mean December 1. Some producers use year/month/day instead, and a brand’s format can vary depending on where the beer was made.

Other breweries use Julian-style dates, which identify the day of the year. For example, 032 means the 32nd day, or February 1. The year may be included in several different ways, so codes such as 26032, 6032, or 03226 can all refer to February 1, 2026. Lagunitas separates the day and year in its “born on” code: 032 6 also means February 1, 2026.

Some codes need extra decoding

Certain breweries use their own systems. Weihenstephaner, for example, uses a four-digit code that combines the final digit of the day, the week number, and the last digit of the year. A code of 1106 could indicate a best-by date of March 1, 2026, if the beer was brewed within the past decade.

Guinness uses a longer code, but its first five characters can help identify the production date. A code beginning with L indicates a lot number. The next four digits give a Julian date, with the first digit representing the final digit of the year. For instance, L6059GH005 suggests production on the 59th day of 2026, or February 28.

Decoding can be further complicated when breweries change their systems. Anheuser-Busch InBev, for example, has updated its codes over time, which means online guides may not always be current. If a date is unclear, contacting the brewery is likely the most reliable way to interpret it.