Almost every component label carries a date code, and many carry a lot code too. Buyers use them to judge how old the parts are, whether they match the paperwork, and whether a shipment comes from one production lot or several. Sellers who understand them can describe their stock more accurately. This guide explains what date codes and lot codes are, how to read them, and why buyers care.
Key takeaways
- A date code shows when a part was made or packed. A common format is four digits for year and week, such as 2312 for week 12 of 2023, but formats vary by manufacturer.
- A lot code identifies the production batch. It is used for traceability when a quality issue appears.
- Many buyers set a maximum date code age. Old date codes are not automatically a problem, but they raise questions about storage and solderability.
What is a date code?
A date code is printed on the part, the reel label or both. It usually indicates the week or month the parts were made or packed. Common patterns include:
- YYWW — two digits for the year and two for the week, for example
2312. - YWW or YW — shorter codes used on small packages with little room for marking.
- Manufacturer-specific codes — letters or symbols that only the manufacturer's documentation explains.
Because formats differ, check the manufacturer's marking guide when a code is unclear. Do not assume that every four-digit number on a label is a date code.
What is a lot code?
A lot code (or batch number) identifies a production run. Parts from the same lot were made under the same conditions. If a defect is found, the manufacturer uses the lot code to find which parts are affected. Reel and tray labels often carry the lot code alongside the date code.
Where do you find them?
- On the reel, tray or tube label, usually with the part number, quantity and manufacturer barcode.
- On the moisture barrier bag label for moisture-sensitive parts.
- On the part body, when the package is large enough for marking.
The codes on the part body, the inner label and the outer label should agree. Mismatches are one of the warning signs buyers look for.
Why do buyers care about date codes?
- Storage and solderability. Older parts may have been stored for a long time. Buyers ask about storage conditions and may ask for solderability testing.
- Customer requirements. Many manufacturers set a rule, for example that date codes must be no older than a certain number of years. The limit depends on the buyer and the product.
- Consistency. Some buyers want all parts in a shipment from a single date code or lot.
- Authenticity. Codes that do not match the manufacturer's format, or differ between part and label, can point to remarked or mixed stock.
How should sellers describe date codes?
- List each date code separately, even for the same part number.
- Copy the code exactly as printed on the label.
- Leave it empty if you do not know, and say so. Guessing causes more trouble than a blank field.
- Note mixed lots if a box contains several date codes.
How StockWake shows date codes
Each lot on a StockWake part page shows its own date code (DC). When a date code is not on record, the page shows "To be confirmed". Lots with different date codes are listed separately.
Prices are not listed on the site. Send us the part numbers and quantities you need and we will email you a quotation in US dollars, including lead time and shipping cost. Quotations are valid for 7 days, subject to prior sale.
Frequently asked questions
Is an old date code a sign of a fake part? Not by itself. Genuine parts can have old date codes, especially end-of-life stock. What matters is storage history, packaging and whether the markings are consistent.
Can I ask for a specific date code? Yes. Put your date code requirement in your request, so it can be checked against the date code of each lot.
What does "DC" mean on a quotation? DC is short for date code.
Need parts with a specific date code? Send us an RFQ or BOM.