Where the dates come from.
Every date-code rule on this site is tied to a source — the manufacturer's own chart, an official lookup, or an authoritative inspector reference — with a date we last verified it. Here is how we source, what we link, and what we never copy.
How we source every rule
Each serial/date-code rule stores its source URL or file, the source date, the value we captured, any caveats, and a last-verified date. We are manufacturer-first: we prefer the manufacturer's own documentation and official lookup, then corroborate with established inspector references (for example, Building Intelligence Center and InspectAPedia), and use the U.S. Consumer Product Safety Commission (CPSC) for recalls.
Confirmed vs estimated
When a code gives an exact result — like A.O. Smith's year-and-week format — we show it as confirmed. When a code is ambiguous, inferred, or community-derived — like Rheem's two-digit year or Rinnai's inspector-documented letter table — we label the result an estimate and point you to the manufacture date printed on the unit or the official lookup.
What we link, and never copy
Recalls
Recall information is tied to the official CPSC notice for that model and serial range, and we route you to the manufacturer's recall line and the official recall lookup. Recalls are safety information — always confirm your specific model and serial with the official source.
Found something wrong?
Spotted a misread code, a stale figure, or a broken source link? Tell us through the contact form and choose 'Correction'. We'd rather hear about it.