code: public DateTime minusHours(int hours) {
          if (hours == 0) {
              return this;
          }
          long instant = getChronology().hours().subtract(getMillis(), hours);
          return withMillis(instant);
      }
docs: Returns a copy of this datetime minus the specified number of hours.
  <p>
  The calculation will subtract a duration equivalent to the number of
  hours expressed in milliseconds.
  <p>
  For example, if a spring daylight savings cutover is from 01:59 to 03:00
  then subtracting one hour from 03:30 will result in 01:30. This is a
  duration of one hour earlier, even though the hour field value changed
  from 3 to 1.
  <p>
  The following three lines are identical in effect:
  <pre>
  DateTime subtracted = dt.minusHours(6);
  DateTime subtracted = dt.minus(Period.hours(6));
  DateTime subtracted = dt.withFieldAdded(DurationFieldType.hours(), -6);
  </pre>
  <p>
  This datetime instance is immutable and unaffected by this method call.
  
  @param hours  the amount of hours to subtract, may be negative
  @return the new datetime minus the increased hours
  @since 1.1