It was based on a custom field that would show an image of the user's country flag and on hover would show the country name and the user's local time. This is what I had in postbit_legacy for 3.5.
Code:
<div class="smallfont">
Location: <img Title="$post[field8] (GMT+$post[timezoneoffset])"
src="http://www.vbaexpress.com/forum/images/flags/$post[field8] 3D.gif"
alt="" align="center" />
This was done a long time ago so I don't really recall how it was setup. Not sure if GMT was a custom variable, I searched the plugins and that text was not found.
--------------- Added [DATE]1374823196[/DATE] at [TIME]1374823196[/TIME] ---------------
{vb:raw post.localtime} seems to do what I want.