Julian date · Expiry

Julian date converter for lot codes and expiry

Read the real manufacture date off the drum, not the receiving date.

Paste a lot code in YYDDD or YYYYDDD, add the shelf life in months, and get the manufacture and expiry dates.

Last updated 2026-09-27. Math runs in your browser, no data leaves your computer.

Paste the lot number exactly as printed. Most chemical and packaging plants that date by Julian code put the year first and the day of the year last, so a five digit block like 24340 is the usual thing to look for.

Letters and separators are fine, and the tool picks out the digit block that decodes to a real day of the year.

Pick the format from the supplier's lot code key when you have it, since a fixed format stops the tool guessing on codes full of digits.

Take shelf life from the product specification or the certificate of analysis, because it runs from the manufacture date and not from the day the goods reached you.

Match the convention your quality manual uses, because the two can sit up to a month apart on the same lot.

Use this when you are writing a lot code key for your own labels, or checking what a supplier should have printed for a given day.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

How the lot code decodes

Expiry mistakes on received goods almost always come from dating the shelf life off the wrong event. Drums can spend two or three months between the filling line and your dock, and a receiving clerk who starts the clock on arrival overstates the life of every lot by the time it spent in transit and in the supplier's warehouse.

A Julian lot code is an ISO 8601 ordinal date: the year, then the day number counted from 1 January as day 001. The tool splits the digits into year and day, checks the day against 365 or 366 for that year, and counts forward from 1 January. Two digit years are read as 2000 to 2099.

Expiry adds whole calendar months to the manufacture date. If the target month is shorter than the start day, the date moves back to that month's last day, and under the end of month convention the date always moves forward to the last day of the expiry month.

Worked example: lot 24340 with a 24 month shelf life

The booking. A pallet of drums reaches the warehouse on 10 March 2025 carrying lot code 24340, and the specification gives a 24 month shelf life. The receiving clerk logs expiry as 10 March 2027, two years from the day the goods arrived, and the stock record looks fine on paper.

The failure. Day 340 of 2024, a leap year, is 5 December 2024, so the real expiry is 5 December 2026, which is 95 days earlier than the record says. Material drawn in early 2027 is past date when a customer audit checks it, and the options are a retest and relabel or a write off.

The fix. Paste 24340 into the tool with a 24 month shelf life and it returns a manufacture date of 5 December 2024 and an expiry of 5 December 2026. The clerk logs that date, first expiry first out picks the lot ahead of newer stock, and it is used well inside its life.

Logging supplier samples and the lots they came from before the bulk order lands? The sample tracking log keeps the lot, the dates and the test result in one place.

Deciding when to reorder so no lot sits long enough to age out? The reorder point calculator sizes safety stock and the order quantity against your lead time.

Frequently asked

What is a Julian date code on a lot number?

In manufacturing, a Julian date code is the year followed by the day of the year, what ISO 8601 calls an ordinal date. The five digit form YYDDD writes 5 December 2024 as 24340, and the seven digit form YYYYDDD writes it as 2024340. Astronomers use the term Julian date for a different day count, which is why some online converters return confusing answers.

How do leap years change the decoding?

In a leap year every day from 1 March onwards has a day number one higher than in a common year, so day 060 is 29 February in 2024 but 1 March in 2025. The tool applies the Gregorian rule, where years divisible by 4 are leap years except century years not divisible by 400.

How is the expiry date calculated from shelf life?

The tool adds the shelf life in whole calendar months to the manufacture date. When the result lands on a day the month does not have, such as 31 June, it moves to the last day of that month. If your quality system dates expiry to the end of the month instead, pick that convention and the tool rounds forward to the month end.

What if the lot code has letters or other digits around the date?

Paste the whole code and the tool looks for a run of 5 or 7 digits that decodes to a valid day of the year. If the plant code also contains digits, check the decoded date against the manufacture date on the certificate of analysis before you rely on it.

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Sourzi shows what official files say. It is not customs or legal advice. For a binding answer, ask a licensed customs broker, a CBP ruling or an Australian Border Force Tariff Advice.

File dates and links are on Data sources.