- I use beforePageLoad for about everything in SSJS, it seems. Did you try that one? If you're doing a full reload that should fire, and it will do so at a point where changes you make will appear in the rendering.
- Alternatively put SSJS in the element that reports the time. That will run during the render and compute your value. Something like this:
<xp:text value="#{javascript:(Now - sessionScope.yourvar);}" />
Hope this helps.