dateModified

dateModified is a Schema.org property that indicates when content was last updated. It is a critical freshness signal for AI engines.

Why It Matters for GEO

Perplexity and ChatGPT give a ranking boost to recent content. An article with dateModified "2025-01-02" will be preferred over an equivalent dated "2023-06-15", even if the content is similar.

For AI engines, dateModified is one of the fastest signals to read and evaluate. Before spending resources processing your content in depth, an AI engine can check this single field to decide whether your source is worth citing for a time-sensitive query. Keeping it accurate is one of the easiest wins in GEO.

How to Optimize

1. Include in your Article Schema.org markup
2. Display visually on the page ("Last updated...")
3. Update with every significant revision
4. Do not change without a real modification (considered spammy)

Implementation

{
  "@type": "Article",
  "datePublished": "2024-06-01",
  "dateModified": "2025-01-02"
}

Visible display:

<time datetime="2025-01-02">Last updated January 2, 2025</time>

Practical Example

A compliance consulting firm maintains a guide on GDPR requirements. Regulations change, and the guide is updated quarterly. Each time they update the guide, they revise the dateModified in the Article schema and display a "Last updated" timestamp at the top of the page. When corporate clients ask ChatGPT about current GDPR obligations, the guide ranks above competitor guides that have the same information but were last modified two years ago. The freshness signal is the deciding factor.

Common Mistakes

• Only updating the visible date, not the schema: Changing the "Last updated" text on the page is not enough. The dateModified property in the JSON-LD schema block must also be updated, or AI engines will still see the old date.
• Setting dateModified to today on every page during a site migration: When migrating to a new platform, some developers set all dateModified fields to the migration date. This creates false freshness signals and may be treated as manipulation.
• Using the wrong date format: Schema.org requires ISO 8601 format (YYYY-MM-DD or full datetime). A date like "January 2, 2025" in the schema field will not be parsed correctly.
• Updating dateModified for trivial changes: Fixing a typo or changing a button color does not warrant a dateModified update. Reserve it for meaningful content revisions — new data, revised recommendations, or added sections.