Electronic Component Date Codes: What They Mean and How to Read Them

Every date code answers one question: when was this part made? Learning to read them takes five minutes — and knowing what they should look like is one of the fastest ways to spot a part that isn't what it claims to be.

Runs entirely in your browser — nothing is sent anywhere. Handles 4-digit YYWW and 3-digit YWW codes, ISO-8601 week math, and week-53 years.

What a date code actually is

A date code is a marking applied at manufacture that encodes when the component was produced. On integrated circuits it's typically laser-marked or inked on the package top; on passives it may appear on the reel label or packaging rather than the part itself; on military components it's a required marking element tied to lot traceability.

Date codes exist because time matters in electronics: solderability of terminations, moisture exposure of plastic packages, shelf-life clauses in purchase contracts, and — for anyone sourcing on the open market — verification that a part's claimed history is physically possible.

The standard format: YYWW

The dominant convention is four digits — two-digit year, two-digit week:

The week number follows the ISO-8601 week calendar: week 1 is the week containing January 4, and weeks run Monday–Sunday. Most years have 52 weeks; years where January 1 lands on a Thursday (or on a Wednesday in a leap year) have 53. That's why a "week 53" code is perfectly genuine for some years and a red flag for others — the decoder above checks this automatically.

Because only two digits carry the year, a code repeats every century: 2436 can't tell you 2024 from 1924 by itself. In practice the package technology, logo era, and part's production lifespan resolve the century instantly.

Variations you'll encounter

Date code vs. lot code — they are not the same thing

A date code tells you when. A lot code (trace code) tells you which production batch — it's the thread the manufacturer can pull to trace a part back to a wafer lot, assembly site, and test run. Many topside markings put both on one line, and some manufacturers fold the date into the lot string rather than marking it separately.

For buyers, the distinction matters in two places. First, traceability: a lot code is what enables meaningful investigation if a quality issue surfaces. Second, documentation: on our Certificates of Conformance, date and lot codes are stated when provided by the manufacturer and required by the customer — which is the industry-honest way to handle data that originates upstream.

Why buyers care: age clauses, storage, and solderability

Many purchase orders carry a date-code restriction — "date code within 24 months" is a common flow-down. It's worth understanding what that clause does and doesn't protect:

• Solderability — termination finishes oxidize over years. Older stock may warrant solderability verification before committing to a production run; that's a test, not a disqualification.
• Moisture sensitivity — plastic-package MSL ratings govern floor life after the bag is opened. Parts stored sealed with desiccant, or re-baked per J-STD-033 before reflow, are handled exactly as the standard intends regardless of calendar age.
• The obsolescence reality — for a part discontinued in 2009, every genuine unit on Earth carries an old date code. A strict recent-date-code clause on an obsolete part is a specification that no authentic part can meet — the conversation to have is about storage history and verification, not the calendar.

Age is a handling consideration, not a verdict. Properly stored components remain usable far beyond typical contractual limits — and the long-lifecycle industries we serve (defense, aerospace, industrial, medical) run on exactly those parts.

Date codes as a counterfeit tripwire

Here's where date-code literacy pays for itself. Counterfeiters have to invent markings, and invented markings collide with physical reality. On our receiving bench, date codes are cross-checked as part of every incoming inspection — and these are the collisions that expose fraud:

• Impossible dates — a date code after the manufacturer discontinued the part, or before the part family existed. A "2023" code on a device whose production ended in 2011 is not a lucky find.
• Mixed codes in sealed packaging — a factory-sealed reel or tube contains one lot. Multiple date codes inside "factory sealed" packaging means the packaging story is false.
• Marking/era mismatch — a date code from one decade on a package style, logo generation, or country-of-origin marking from another.
• Format the manufacturer never used — a YYWW code on a product line that always embedded dates in lot strings, or vice versa.
• Too-perfect uniformity — remarked lots sometimes carry a single fabricated code across parts whose mold and pin-print details visibly differ.

These checks are part of our documentation and external visual inspection — microscopy to 3000×, marking-permanency testing, and pin-print comparison against known-good references — with deeper screens (XRF, FTIR, X-ray, decapsulation, electrical test) performed by accredited independent laboratories to our protocol when a lot warrants it. The full flow is documented in our quality program.

Quick key: reading a typical IC marking

Layouts vary by manufacturer and package size; small packages may abbreviate the part number itself into a marking code that requires the manufacturer's topside-marking decoder to interpret.