Document.timeline

The timeline readonly property of the Document interface represents the default timeline of the current document. This timeline is a special instance of DocumentTimeline that is automatically created on page load.

This timeline is unique to each document and persists for the lifetime of the document including calls to Document.open().

The time values for this timeline are calculated as a fixed offset from the global clock such that the zero time corresponds to the navigationStart moment plus a signed delta known as the origin time. Prior to establishing the navigationStart moment, the document timeline is inactive.