PHP Class for handling time zone conversions.

TimeShift.php

<?php

class TimeShift {
  
	public static $zones = array(
		"America/New_York" 				=> "Eastern",
		"America/Chicago" 				=> "Central",
		"America/Denver" 				=> "Mountain",
		"America/Phoenix" 				=> "Arizona",
		"America/Los_Angeles" 			=> "Pacific",
		"America/Anchorage" 			=> "Alaska",
		"Pacific/Honolulu" 				=> "Hawaii",
	);

	public static function utcNow()
	{
		$date = new DateTime("now", new DateTimeZone('UTC'));
		return $date->getTimestamp();
	}

	// convert a local date string along with a specified timezone into a UTC timestamp for storage
	public static function getUTCTimestamp($localDateString, $localTimeString, $localTimezone)
	{
		$date = new DateTime($localDateString . ' ' . $localTimeString, new DateTimeZone($localTimezone));
		$date->setTimezone(new DateTimeZone('UTC'));
		return $date->getTimestamp();
	}

	// take a stored UTC timestamp along with a specified timezone and return a local datetime object
	public static function getLocalDateTime($utcTimestamp, $localTimezone)
	{
		$date = new DateTime("now", new DateTimeZone('UTC'));
		$date->setTimestamp($utcTimestamp);
		$date->setTimezone(new DateTimeZone($localTimezone));
		return $date;
	}

	public static function getPrintableZone($timezone)
	{
		return self::$zones[$timezone];
	}
}