    public static function _date2timestamp( $datetime, $wtz=null ) {
      if( !isset( $datetime['hour'] )) $datetime['hour'] = 0;
      if( !isset( $datetime['min'] ))  $datetime['min']  = 0;
      if( !isset( $datetime['sec'] ))  $datetime['sec']  = 0;
      if( empty( $wtz ) && ( !isset( $datetime['tz'] ) || empty(  $datetime['tz'] )))
        return mktime( $datetime['hour'], $datetime['min'], $datetime['sec'], $datetime['month'], $datetime['day'], $datetime['year'] );
      $output = $offset = 0;
      if( empty( $wtz )) {
        if( iCalUtilityFunctions::_isOffset( $datetime['tz'] )) {
          $offset = iCalUtilityFunctions::_tz2offset( $datetime['tz'] ) * -1;
          $wtz    = 'UTC';
        }
        else
          $wtz    = $datetime['tz'];
      }
      if(( 'Z' == $wtz ) || ( 'GMT' == strtoupper( $wtz )))
        $wtz      = 'UTC';
      try {
        $strdate  = sprintf( '%04d-%02d-%02d %02d:%02d:%02d', $datetime['year'], $datetime['month'], $datetime['day'], $datetime['hour'], $datetime['min'], $datetime['sec'] );
        $d        = new DateTime( $strdate, new DateTimeZone( $wtz ));
        if( 0    != $offset )  // adjust for offset
          $d->modify( $offset.' seconds' );
        $output   = $d->format( 'U' );
        unset( $d );
      }
      catch( Exception $e ) {
        $output = mktime( $datetime['hour'], $datetime['min'], $datetime['sec'], $datetime['month'], $datetime['day'], $datetime['year'] );
      }
      return $output;
    }

The software constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.