public RrdGraphDef(){
  setTimeSpan(Util.getTimestamps(DEFAULT_START,DEFAULT_END));
}

public RrdGraphDef ( ) { setTimeSpan ( Util . getTimestamps ( DEFAULT_START , DEFAULT_END ) ) ; }
creates rrdgraphdef object and sets default time span ( default ending time is ' now ' , default starting time is ' end - 1day ' .
