UTC_TIMESTAMP() to user defined timezone? - unix-timestamp

Question

I am storing timestamps in my db using UTC_TIMESTAMP().
I want to output them based on user selected timezone. I tried writing a small function to do this, however, it does not output correctly.
// Date/time converter
function convertTZ($date, $tz, $tzFormat)
{
$date = new DateTime($date);
$date->setTimezone(new DateTimeZone($tz));
return $date->format($tzFormat);
}
echo $_SESSION['dtCurrLogin'].'<br />';
echo convertTZ($_SESSION['dtCurrLogin'], 'UTC', 'F j, Y # g:i:s a e');
dtCurrLogin from db = 2013-09-12 01:23:45
the above outputs :
2013-09-12 01:23:45
September 12, 2013 # 5:23:45 am UTC
Obviously this is not correct as I went from UTC to UTC so they should be equal. If I change to output EST then it shows 1:23:45 am, but of course that would not be right either.

Answer 1

Didn't realize I needed to specify incoming timezone... using the following worked for me...
function convertTZ($date_time, $from_tz, $to_tz, $format_tz)
{
$time_object = new DateTime($date_time, new DateTimeZone($from_tz));
$time_object->setTimezone(new DateTimeZone($to_tz));
return $time_object->format($format_tz);
}