function _stepdate( &$date, &$timestamp, $step=array( 'day' => 1 )) {
    foreach( $step as $stepix => $stepvalue )
      $date[$stepix] += $stepvalue;
    $timestamp  = $this->_date2timestamp( $date );
    $date       = $this->_date_time_string( date('Y-m-d H:i:s', $timestamp ), 6);
    foreach( $date as $k => $v ) {
      if( ctype_digit( $v ))
        $date[$k] = (int) $v;
    }
  }
function _stepdate( &$date, &$timestamp, $step=array( 'day' => 1 )) {
    foreach( $step as $stepix => $stepvalue )
      $date[$stepix] += $stepvalue;
    $timestamp  = $this->_date2timestamp( $date );
    $date       = $this->_date_time_string( date('Y-m-d H:i:s', $timestamp ), 6);
    foreach( $date as $k => $v ) {
      if( ctype_digit( $v ))
        $date[$k] = (int) $v;
    }
  }
function _stepdate ( & $ date , & $ timestamp , $ step = array ( 'day' => 1 ) ) { foreach ( $ step as $ stepix => $ stepvalue ) $ date [ $ stepix ] += $ stepvalue ; $ timestamp = $ this -> _date2timestamp ( $ date ) ; $ date = $ this -> _date_time_string ( date ( 'Y-m-d H:i:s' , $ timestamp ) , 6 ) ; foreach ( $ date as $ k => $ v ) { if ( ctype_digit ( $ v ) ) $ date [ $ k ] = ( int ) $ v ; } }
step date, return updated date, array and timpstamp

@author Kjell-Inge Gustafsson <ical@kigkonsult.se>
@since 2.2.15 - 2007-11-12
@param array $date, date to step
@param int $timestamp
@param array $step, default array( 'day' => 1 )
@return void
step date return updated date array and timpstamp