Food Safety Food Handler

Decoding Date Codes: How Do I Read Julian Codes and Date Marks?

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Trust20 Contributors • 10 minute read

We’ve all encountered the horror of reaching into the back of the fridge, freezer, or pantry only to find something forgotten that might have gained sentience. You squint at the mark in the corner–is that a date? What does it mean? This situation takes on much higher stakes in a commercial kitchen!

A lot goes into keeping a kitchen safe, clean, and running smoothly, and date codes are an essential element of the process. Everyone on your team should know how to read date codes and consistently write date marks on any repackaged foods or leftovers.

Date codes and date marking help staff make decisions about which ingredients are the freshest to use, which should be disposed of to avoid foodborne illness (keeping food out of the temperature danger zone is still the most effective way to prevent this), and how you should organize foods for ease of access.

Here’s how to train your staff to maximize freshness without wasting food–in a way that won’t stress them out further in a busy kitchen.

Understanding date codes

Date codes and the law

How to date mark TCS foods in the kitchen

What happens if it goes wrong? 

It’s not spy stuff 

Understanding date codes 

Two different kinds of dating appear on product labels: “open dating” and “closed dating.” Each one serves different purposes, so it’s important for staff to understand what each one means. 

Open date codes

“Open dating” is a calendar date from the food product’s manufacturer or retailer that provides information about the estimated time the product will be at its best. For a kitchen, this means the window of time you should use these ingredients to prepare dishes that need them to be at their peak.

Reaching the end of this period doesn’t mean the food is unsafe, but it has passed this ideal quality window. After that date, you can still use these products for dishes that don’t require ingredients to be at their absolute freshest. For example, fresh eggs fry or poach better, while older eggs may work better in certain baked goods.

You can also find these date codes on food products like meat, poultry, and dairy.  

Closed date codes

“Closed dating,” on the other hand, is a series of letters and/or numbers instead of a date. The manufacturer applies these codes to let you know when–the date and time–the manufacturer made the food product. Closed date codes include Julian codes, which show the number of days since the beginning of the calendar year. For example, a Julian date of 031 would mean January 31st, and 365 would mean December 31st.1

You can usually find these date codes on shelf-stable packaging (and this is why you can often reach into your great uncle’s pantry and find a can of beans from the turn of the century). 

Phrases commonly used on packaging 

Aside from date codes, there are familiar phrases on many packaging stating when you should use, sell, or freeze a food product. These are not regulated terms, which is one reason they vary across food products and brands. 

Common phrases, as indicated by the USDA, include: 

  • “Best if used by/before”: use before this date to ensure the freshest quality of this food product; it’s not about food safety.  

  • “Sell-by”: used by retail food establishments to know how long to display a food product when it is still at its peak quality; it’s not about food safety.  

  • “Use-by”: use before this date to ensure the best quality; this is only about food safety if it’s on infant formula.  

  • “Freeze-by”: freeze by this date to ensure the food remains at its best quality; it’s also not about food safety.2

Like the date codes, these phrases also don’t mean a food is unsafe past these dates, but that the food product is no longer guaranteed to be at its freshest outside of these dates. Continuing to use them in dishes that require fresh ingredients could result in serving lower-quality food to customers. 

Why this is important 

The only food product that is required to have an expiration date (which means it is no longer safe to consume past that date) is infant formula. All other food date codes suggest food quality, not food safety.

It’s essential to understand this distinction so staff are working to serve dishes made with the freshest available ingredients and using ingredients that are still safe but not at their peak in other dishes where the customers won’t notice a difference. 

This way, you maximize both the taste for customers and the bottom line for your budget. 

Date codes and the law 

The FDA did not specifically update rules around date codes in the 2022 Food Code.3 Federal regulations require a date code to be present for traceability but do not specify how it's written (see the different phrases listed above). As mentioned earlier, infant formula is the only food product federal law explicitly requires dating around safety. 

For other food products, The USDA’s jurisdiction under the Food Safety and Inspection Service (FSIS) states that manufacturers may voluntarily apply dates on meat, poultry, and egg products and that those labels cannot be misleading. Calendar dates must have the day and month present to comply with FSIS regulations.

Frozen and shelf-stable food products must also list the year to comply with regulations (since these foods last much longer) and a phrase next to it explaining that the date is a “best by” date and does not indicate anything about food safety. 

Time and Temperature Controlled for Safety (TCS) 

Time and Temperature Controlled for Safety (TCS) foods are more likely than others to grow pathogens if not kept at a safe temperature, making them unsafe to eat and causing foodborne illness. TCS foods include meat, poultry, eggs, dairy, shellfish, and less obvious foods like cooked pasta, rice, or tofu. Properly marking these foods with the date when first opening the packaging, storing leftover ingredients, and freezing them is key to ensuring their safety.

This practice is the second kind of date coding–date marking–your team must understand for quality and food safety purposes! 

How to date mark TCS food in your kitchen 

Each kitchen must determine which system they use to date mark foods–especially TCS foods. You and your team can develop a shorthand showing when you have received or opened a food and when it needs to be consumed by. You can use a combination of dates and/or color coding to communicate a food product’s lifespan quickly.

Your chosen system must be clear, consistent, and reliable throughout your kitchen. If the staff mixes up when something is “best by” vs. when it should be “thrown out by,” you have the potential for foodborne illness. If the reverse is true, staff may be throwing out food that is still safe to use, leading to food waste and an impact on your bottom line.

The date marking your kitchen uses should be clear and consistent in its location on food products so staff doesn’t have to search an entire package to find the information they’re looking for, especially during a rush. 

Below is an example from the Wisconsin Food Code of what date marking might look like.4

  1. If you cook a turkey on the morning of October 1st, hold it under refrigeration for two days, and then freeze it, the clock pauses on day three. Thawing the turkey on October 10th restarts the clock; it needs to either be consumed or discarded no later than midnight, October 14th:


Shelf life/day


Oct. 1


Cook/cool/cold hold

Oct. 2


Cold hold

Oct. 3

(freezing pauses the clock)


Oct. 10


Thaw under refrigeration

Oct. 11


Cold hold/consume

Oct. 12


Cold hold/consume

Oct. 13


Cold hold/consume

Oct. 14


Cold hold/consume 

Oct. 15



All of this should be clearly marked on the packaging the turkey is stored in for the rest of the kitchen staff to understand. Marking should include the day you cooked the turkey, how long it was stored cold, when you thawed it, and the date it needs to be consumed and/or discarded. 

What happens if it goes wrong? 

Getting this wrong means potentially getting customers sick, leading to a negative impact on the restaurant. That could mean anything from bad reviews and a temporary drop in business to a lawsuit and complete business closure. The latter can happen if there’s a severe enough case of foodborne illness that an investigation traces back to your kitchen. 

To avoid this, comprehensive training for kitchen staff around reading and understanding date codes and your system for date marking is vital. 

It’s not spy stuff  

Understanding date coding doesn’t require an advanced degree in spycraft, but it does require thorough training and regular check-ins to ensure your entire team retains the information. It can be helpful to look for ways to make training fun, including holding effective stand-ups.

Always ensure new team members get a rundown of how your establishment handles date codes and date marking–and check in with long-time staff to see if they have any misconceptions or concerns about your establishment’s procedures.

Remember, date codes are a direct reflection of food quality, and your date marking practices will help your kitchen run smoothly–while protecting food safety. You don’t need to create a secret code or practice any spycraft when it comes to date codes or markings.

Just keep it simple!

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  1. State of Oregon: Decoding Food Product Dates

  2. USDA: Food product dating 

  3. Summary of Changes in the 2022 FDA Food Code

  4. Wisconsin Food Code: Date Marking of Ready-to-Eat Time-Temperature Control for Safety Foods