/**
* TimeStamp wrapping the PEAR Date class.
*/
class TimeStamp {                     
	/**
	* @var Date
	*/
	var $_Date = null;                  
 
	/**
	* @desc create a new TimeStamp for obj-instance fields
	* @param $time (optional) - leave blank to get NOW() timestamp, or pass in a unix timestamp or datetime string if you like
	* @param $isUTC (optional) - set TRUE if the passed in $time is UTC (e.g. comes from a DB field that's maintained in UTC)
	*/
	public function __construct( $time = null, $isUTC = false ){        
 
		if( !class_exists('Date') ){
			throw new Exception( 'PEAR Date not available' );
		}
 
		$this->_Date = new Date();
 
		if( !is_null($time) ){  
			$this->_Date->setDate( $time );
			if( $isUTC ){
				$this->_Date->setTZbyID( 'UTC' );     
			}  
		}        
 
		$this->_Date->toUTC();             
	}     
 
	public function __toString(){
		return $this->_Date->format( '%Y-%m-%d %H:%M:%S' ); // this is UTC, as we store it in server logs and the DB for example
	}
 
	public function getLocalized( $tz=null ){
 
		$rd = new Date( $this->_Date );
 
		if( $tz ){
			$rd->convertTZbyID( $tz ); // convert to the user's timezone... if none set, the system timezone will be used
		}else{
			$rd->convertTZ( Date_TimeZone::getDefault() ); // convert to the default system timezone
		}
 
		return $rd->format( '%Y-%m-%d %H:%M:%S' );
	}
 
	public function getDateString(){  
		global $global;     			
		return $this->_Date->format('%Y-%m-%d');
	}      
 
	public function getTimeString(){         
		global $global;     			
		return $this->_Date->format('%H:%i:%s');
	}   
 
	public function add( $Y=0, $M=0, $D=0, $h=0, $m=0, $s=0 ){			         			           
		$span = new Date_Span( "$Y-$M-$D $h:$m:$s" );											 
		$this->_Date->addSpan( $span );
	}      
 
	public function sub( $Y=0, $M=0, $D=0, $h=0, $m=0, $s=0 ){   			         			           
		$span = new Date_Span( "$Y-$M-$D $h:$m:$s" );											 
		$this->_Date->subtractSpan( $span );
	}
 
	public function getAge(){
		return $this->getAgeInYears();
	}     
 
	/**
	* Get the age of this date in years. This routine simply gets the
	* age in months, devides it by 12 and rounds down to whole years.
	*/
	public function getAgeInYears(){
		$months = $this->getAgeInMonths();
		$years = intval($months/12);
		return $years;
	}
 
	/**
	* Get the age of this date in months. The special thing is that a
	* monthely age is discrete by days. For example, on your birthday you
	* become one month or year older immediately, no matter if you were
	* born 1am or 11pm.
	* 
	* The special case of trespassing the turn of the year is implicitely
	* handled by adding the delta-months (dMonth) to the months of the
	* delta-years*12.
	*/
	public function getAgeInMonths(){
		$now = new Date();
		$now->toUTC();
		$dYear = $now->year - $this->_Date->year;
		$dMonth = $now->month - $this->_Date->month;
		$dDay = $now->day - $this->_Date->day;
 
		$months = $dYear*12 + $dMonth;
		if( $dDay<0 ){      
			$months--;
		}       
 
		return $months;
	}
 
	/**
	* All of the getAgeInXxx routines below just rely on the PEAR classes
	* Date and Date_Span. A Date_Span is created from $this->Date to
	* now (new Date() == now). Then the integer-part of Date_Span::toDays(),
	* toHours(), toMinutes() or toSeconds() is returned. Be aware we herein
	* are limited to 32 bit again and shouldn't getAgeInSeconds of
	* TimeStamps older than round about 63 years.
	*/
	public function getAgeInWeeks(){  
		$days = $this->getAgeInDays();                   
		return intval($days/7);
	}
 
	public function getAgeInDays(){   
		$span = new Date_Span();
		$span->setFromDateDiff( $this->_Date, new Date() );
		return intval($span->toDays()); 
	}
 
	public function getAgeInHours(){
		$span = new Date_Span();
		$span->setFromDateDiff( $this->_Date, new Date() );
		return intval($span->toHours());
	}
 
	public function getAgeInMinutes(){
		$span = new Date_Span();
		$span->setFromDateDiff( $this->_Date, new Date() );
		return intval($span->toMinutes());
	}  
 
	public function getAgeInSeconds(){
		$span = new Date_Span();
		$span->setFromDateDiff( $this->_Date, new Date() );
		return intval($span->toSeconds());
	}                             
}

class ExampleClass {
	var TimeStamp;
	var PayLoad;
}
 
$object = new ExampleClass();
$object->PayLoad = "This is an example without sense.";
$object->TimeStamp = new TimeStamp( "1980-02-29", TRUE ); // UTC
echo $object->TimeStamp->getLocalized(); // system timezone!
echo $object->TimeStamp->getLocalized( 'UTC+2' ); // Central European Summer Time
// output:
// 1980-02-29 00:00:00
// 1980-02-29 02:00:00
 
// when not taking care of timezones, the timestamp will
// accept PHPs system timezone format as input and provide
// UTC to database and users, like that's the most neutral
// way to handle time!
$object->TimeStamp = new TimeStamp( "1980-02-29" ); // system timezone
echo $object->TimeStamp; // UTC!
// output (when system timezone is UTC+2):
// 1980-02-28 22:00:00
 
// To build an SQL statement using UTC format
// just use the TimeStamp as a string:
$sql = "INSERT INTO table SET TimeStamp=".addslashes($object->TimeStamp);