CDatabase::DatetimeToTimestampFunction

public function DatetimeToTimestampFunction($fieldName)
{
	$timeZone = "";
	if (CTimeZone::Enabled())
	{
		static $diff = false;
		if($diff === false)
			$diff = CTimeZone::GetOffset();

		if($diff <> 0)
			$timeZone = $diff > 0? "+".$diff: $diff;
	}
	return "extract(epoch FROM $fieldName)".$timeZone;
}