Date triangulation

Google detects a 'date lie' by comparing three different signals for a page's date. (1) The visible date in the article (bylineDate) is easy to fake. (2) The date from URL, markup or timestamp (syntacticDate) is 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 sees 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 that a date is honest.

Three date fields, compared with each other. 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: anyone who disguises an old document as 'new' by changing the date is detected.

Update a date only if the content was genuinely updated too. This applies especially to seasonal content. 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.