Virtually every page-load milestone is contained in the browser's performance.timing object. This includes the following milestones (and more):

- server request time
- redirect start time
- the time the browser starts rendering the page
- the time when the page is interactive to the user
- the time when the page is fully loaded.

Using some pretty simple JavaScript, any of these timestamps can be captured in your analytics tool of choice. You will want to make sure that the values you capture are representative of what your company considers to be the full and accurate view of page load time. A code sample exists on the following blog post that you can adjust in any way that you choose, and then the data made available can be passed to your analytics tool using your tag management system:

http://analyticsdemystified.com/google-analytics/hard-truth-measuring-page-load-time/ (Link 1)

RELATED: Link 1