The navigationStart property must return the time immediately after the user agent finishes prompting to unload the previous document. If there is no previous document, this property must return the same value as fetchStart.
An Integer value that represents the time immediately after the user agent finishes prompting to unload the previous document.
- Navigation Timing, Section 4.2
The value reported by the navigationStart property represents the number of milliseconds between the recorded time and midnight January 1, 1970 (UTC).
The following example shows how to calculate the time required to load the document, which this example defines as the time between the initial navigation action and the time when the document is presented to the user.
var oTiming = window.performance.timing; var iTimeMS = oTiming.msFirstPaint - oTiming.navigationStart;