code: public static Duration convertUnits(double duration, TimeUnit fromUnits, TimeUnit toUnits, ProjectProperties defaults)
     {
        return (convertUnits(duration, fromUnits, toUnits, defaults.getMinutesPerDay().doubleValue(), defaults.getMinutesPerWeek().doubleValue(), defaults.getDaysPerMonth().doubleValue()));
     }
docs: This method provides an <i>approximate</i> conversion between duration
  units. It does take into account the project defaults for number of hours
  in a day and a week, but it does not take account of calendar details.
  The results obtained from it should therefore be treated with caution.
  
  @param duration duration value
  @param fromUnits units to convert from
  @param toUnits units to convert to
  @param defaults project properties containing default values
  @return new Duration instance