Date triangulation

Google checks a page's date by comparing three different signals: (1) the visible date in the article (bylineDate — easy to fake), (2) the date from URL, markup or timestamp (syntacticDate — also easy to manipulate), (3) the date inferred from the text content (semanticDate — can only be changed through genuine content updates). When the three don't agree, Google detects a 'date lie'.

Three independent date signals with different costs to fake — the system uses the difference between easy-to-fake and hard-to-fake signals to verify date honesty.

bylineDate = a visibly stated date (cheaply faked); syntacticDate = extracted from URL/markup/timestamp (cheaply faked); semanticDate = inferred from the content (only fakeable through genuine updating). The cross-check exposes date lies. [B fields, O date determination]

Trust is primary and the only primary signal in the entire freshness class — date deception is a direct breach of trust: disguising an old document as 'new' by changing the date is detected.

Especially for seasonal content: a date may only be updated if the content was genuinely updated too. Merely changing the date in the CMS without substantive changes — a widespread SEO practice — is detected via semanticDate and damages the trust score. Content must be substantially revised.