private function dateDiff() : DateInterval
    {
        if (null === $this->dateDiff) {
            $this->dateDiff = $this->from->withTimeAtMidnight()->diff($this->until->withTimeAtMidnight());
        }
        
        return $this->dateDiff;
    }
private function dateDiff() : DateInterval
    {
        if (null === $this->dateDiff) {
            $this->dateDiff = $this->from->withTimeAtMidnight()->diff($this->until->withTimeAtMidnight());
        }
        
        return $this->dateDiff;
    }
private function dateDiff ( ) : DateInterval { if ( null === $ this -> dateDiff ) { $ this -> dateDiff = $ this -> from -> withTimeAtMidnight ( ) -> diff ( $ this -> until -> withTimeAtMidnight ( ) ) ; } return $ this -> dateDiff ; }
A diff between the two dates with times set to midnight to guarantee resolution to whole days.

@return DateInterval
A diff between the two dates with times set to midnight to guarantee resolution to whole days .