Julian Date Converter
Decode a 5-digit YYDDD manufacturing or expiration code into a calendar date, or generate one from any date.
How the 5-digit code works
A YYDDD Julian date code packs a 2-digit year and a 3-digit day-of-year into 5 digits — no separators, no month. "26045" is year '26 (2026), day 45 of that year, which lands on February 14. Manufacturing and military logistics have used this ordinal-day format for decades because it's compact and sorts correctly as plain digits; food and beverage packaging picked it up for the same reason canned goods, snack bags and bottled drinks often stamp a run of digits instead of a written date.
Reading a code straight off a package
Most 5-digit codes stamped on packaging are exactly this format, but manufacturers sometimes append extra characters for a plant number, production line or shift — for example "L4 25100" or "25100A" — that this tool doesn't try to parse. Strip it down to the 5 numeric digits before decoding, and if the resulting date is obviously wrong (in the future for a "best by" stamp, or decades in the past), try the other century option before assuming the code uses a different scheme entirely.
Frequently asked questions
What does a 5-digit Julian date code like 25100 mean?
The first two digits are the year and the last three are the day of that year, counting from January 1st as day 001. 25100 means year '25 (2025), day 100 — April 10, 2025.
How does the converter know which century a 2-digit year means?
It can't know for certain — manufacturers don't follow one universal rule. This tool defaults to the 2000s since most codes you'd decode today are recent, but switch the century toggle to the 1900s if the product is clearly older or the resulting date doesn't make sense.
My product's code doesn't look like 5 digits — will this still work?
Not reliably. Some manufacturers pad the code with a plant, line or shift letter, use a 4-digit year+day variant, or use a proprietary lot-code scheme with no public key at all — this tool only decodes the standard 5-digit YYDDD format. If in doubt, the safest fallback is the "best by" or "use by" date printed in plain text elsewhere on the package.
Is this the same as an astronomical Julian day number?
No, different thing despite the shared name. Astronomers' Julian Day Number is a single ever-increasing count of days since 4713 BC, used for calculating time spans across centuries. The YYDDD code here — sometimes called "ordinal date" to avoid the mix-up — just restarts at day 001 every January 1st, which is what manufacturing and military date stamps actually use.