code: public DateTime plusMinutes(int minutes) {
          if (minutes == 0) {
              return this;
          }
          long instant = getChronology().minutes().add(getMillis(), minutes);
          return withMillis(instant);
      }
docs: Returns a copy of this datetime plus the specified number of minutes.
  <p>
  The calculation will add a duration equivalent to the number of minutes
  expressed in milliseconds.
  <p>
  The following three lines are identical in effect:
  <pre>
  DateTime added = dt.plusMinutes(6);
  DateTime added = dt.plus(Period.minutes(6));
  DateTime added = dt.withFieldAdded(DurationFieldType.minutes(), 6);
  </pre>
  <p>
  This datetime instance is immutable and unaffected by this method call.
  
  @param minutes  the amount of minutes to add, may be negative
  @return the new datetime plus the increased minutes
  @since 1.1