Sorry, I didn't see this post previously. Here is what Vera told me when I asked about changing mine from US Eastern to US Mountain time...
If you open 'var_definition_example.php' you can find there an example:
// save new date with time shift in seconds (3600 - 1 hour)
//$va_time_shift = 0;
So you need to open the file 'var_definition.php' and add the following line:
$va_time_shift = 7200;
or
$va_time_shift = -7200;
Hope this helps!