Coded expiration dates are the strings of letters and numbers stamped on cans, bottles, and packages that don’t look like a normal calendar date. Unlike a clear “Best if Used By 06/15/2026” label, these codes were designed for manufacturers to track production batches, not for consumers to read. There is no single universal system, but most coded dates follow a handful of common formats once you know what to look for.
Open Dates vs. Closed Dates
The food industry uses two broad categories of date labeling. “Open dating” is the kind you can read at a glance: a calendar date paired with a phrase like “Sell-By,” “Best if Used By,” or “Use-By.” “Closed dating” is the coded kind, a series of letters and numbers applied by the manufacturer to identify the date and time of production. According to the USDA’s Food Safety and Inspection Service, these closed codes are primarily meant to help manufacturers rotate stock and locate products during recalls. They were never designed for consumers to interpret as freshness dates.
That said, many products carry only a closed code and nothing else, which is why so many people end up searching for how to crack them.
The Julian Date System
The most common format in coded dates is the Julian date, which represents the day of the year as a three-digit number from 001 (January 1) to 365 (December 31). January 15 would be 015. March 1 in a non-leap year would be 060. December 31 would be 365. This system shows up constantly on canned goods, bottled beverages, and household products.
The Julian date is usually paired with a year indicator. Sometimes the year appears as a full four digits (2024), sometimes as two digits (24), and sometimes as a single digit (4). The year digit might come before or after the Julian date depending on the manufacturer. So a code reading “4187” could mean the 187th day of 2024, which is July 5. A code reading “24187” means the same thing with the year spelled out more clearly.
How to Convert a Julian Date
You don’t need to memorize each day of the year. A quick reference: January covers days 001 through 031, February runs 032 through 059, March is 060 through 090, and so on. The easiest approach is to search “Julian date calendar” online to find a chart for the current year, or simply count forward from the start of the month you think the number falls in. If the code reads 099, you know it’s in April (April 1 is day 091 in a non-leap year), so day 099 is April 9.
How to Read Clorox and Household Product Codes
Household disinfectants and bleach are worth special attention because their effectiveness genuinely declines over time. Clorox bleach, for example, has a shelf life of about one year from the date of manufacture, after which the active ingredients lose potency.
Clorox uses a specific code format. Take the example code G18099. The first two characters (G1) identify the manufacturing plant and aren’t relevant to dating. The third character (8) represents the year, in this case 2018. The remaining three digits (099) are the Julian date, meaning day 99 of the year, or April 9. So this bottle was made on April 9, 2018, and its effective shelf life would extend to roughly April 2019. Other cleaning product manufacturers use similar structures, though the position of the year digit and plant codes may shift. Look for a single digit that makes sense as a recent year, then check if the remaining digits fall between 001 and 365.
Common Code Formats on Canned and Packaged Food
Canned goods are required to display either a code or the date of canning, and many manufacturers use both a closed code and an open “Best if Used By” date. When only a closed code is present, it typically contains a combination of the manufacturing plant identifier, the year, the Julian date, and sometimes a shift or line number. The plant identifier is often a letter or pair of letters at the beginning or end of the string.
Some manufacturers use a month-day-year format but abbreviate it in ways that look confusing. A code like “FEB2526” might mean February 25, 2026. Others use a letter to represent the month: A for January, B for February, C for March, and so on through L for December. Under this system, a code starting with “D” refers to April. If you see D2524, that could mean April 25, 2024.
The frustrating reality is that there is no single book or reference that translates every manufacturer’s code system. The USDA has confirmed this. Each company chooses its own format, and the codes can vary even between product lines from the same brand. When a canned product has no readable open date and you can’t decode the closed date, the most practical option is to contact the manufacturer directly. Most have a customer service number printed on the label, and representatives can decode the specific can you’re holding.
What “Sell-By,” “Best By,” and “Use-By” Actually Mean
When a product does display an open date, the phrasing matters more than most people realize. A “Sell-By” date is directed at the store, not you. It tells retailers when to pull the product from shelves, but the food is typically still safe to eat for days or even weeks afterward depending on the item. A “Best if Used By” date refers to quality and flavor, not safety. Food past this date may taste slightly different but isn’t automatically dangerous. A “Use-By” date is the strongest recommendation, indicating the last date the manufacturer stands behind the product’s peak quality.
None of these phrases are federally standardized for most foods. Infant formula is the notable exception, where expiration dating is legally required and should be followed strictly. For everything else, these dates reflect the manufacturer’s quality judgment, not a hard safety cutoff.
Cosmetics and Personal Care Products
Beauty and skincare products use their own system. In the European Union and increasingly on products sold worldwide, you’ll find the Period After Opening (PAO) symbol: a small graphic of an open jar with a number printed on or next to it, like “12M” or “24M.” This tells you how many months the product remains effective after you first open it. A moisturizer labeled 12M should be used within 12 months of opening, regardless of when you bought it.
The PAO symbol doesn’t help with unopened products sitting in a drawer. For those, look for a batch code, usually a string of letters and numbers printed or embossed on the bottom or back of the packaging. Several free websites (CheckCosmetic and CheckFresh are the most widely used) let you enter the brand name and batch code to find the manufacturing date. From there, most unopened cosmetics are considered good for two to three years, though preservative-free or natural formulations may have shorter windows.
Practical Tips for Decoding Any Product
Start by looking for a string that could be a Julian date: three digits between 001 and 365. Then look for an adjacent single digit or two-digit number that makes sense as a year. Ignore any letters at the very beginning or end of the code, as these usually indicate the plant or production line. If two separate codes appear on the package, one is often the lot number for recall tracking and the other is the date code. The shorter of the two is more likely the date.
For food storage questions beyond date codes, the USDA’s FoodKeeper app provides storage timelines for more than 400 food and beverage items. It won’t decode a specific manufacturer’s code, but it can tell you how long a particular type of food is generally safe to keep in your pantry, refrigerator, or freezer, which is often more useful than the code itself.
If you’re holding a product right now and can’t crack the code, your fastest path to an answer is the manufacturer’s customer service line. Give them the full code and they can tell you exactly when it was made and when it expires. No guesswork needed.