PHP: Timezone Adjustment

# Timezone Adjustments
function timezone_get_gmz( $input ){
	if( !isset($input) )
		$input = time();
	// return offset of unix time - offset of time
	// date O returns system's timezone offset: -0500.. -0800..
	// therefore, hours turn from 3600 to 36
	return $input-(date('O')*36);
}
function timezone_convert($time, $hoursOffset = -5){
	// default of EST
	// - hoursOffset because offset for EST is 5.. but you subtract it
	// this will multiply GMZ time by the hours offset defined
	return timezone_get_gmz($time)+(3600*(-$hoursOffset));
}
function timezone_makeDate ($format='',$input){
	global $user;
 
	// check for input 		:: Default = time ()
	// convert input to unix if not a number
	// get user timezone if it's set
	// apply timezone time to time and return in format of date
 
	if( !isset( $input ) )
		$input = time();
	if( !is_numeric( $input ) )
		$input = strtotime($input);
	if( isset($user->personal_data['timezone']) )
		$timezone = $user->personal_data['timezone'];
	else
		$timezone = 5;
	if ($format=='')
		return timezone_convert($input,$timezone);
	else
		return date($format,timezone_convert($input,$timezone) );
}