$gmt will return the number of seconds elapsed since 00:00:00 GMT, January 1, 1970, where $ctime adjusts by adding/subtracting the timezone to the result of $gmt.
I'm in EST so I need to subtract hours from GMT. $timezone returns your current timezone setting in seconds.
Proof of concept:
//echo -a $asctime($ctime) vs. $asctime($calc($gmt - $timezone))
Result:
Fri Jan 31 19:34:15 2014 vs. Fri Jan 31 19:34:15 2014
Hope this helps point you in the right direction to get the proper timestamp you require.
