code: public LocalDateTime plusWeeks(long weeks) {
          LocalDate newDate = date.plusWeeks(weeks);
          return with(newDate, time);
      }
docs: Returns a copy of this {@code LocalDateTime} with the specified number of weeks added.
  <p>
  This method adds the specified amount in weeks to the days field incrementing
  the month and year fields as necessary to ensure the result remains valid.
  The result is only invalid if the maximum/minimum year is exceeded.
  <p>
  For example, 2008-12-31 plus one week would result in 2009-01-07.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param weeks  the weeks to add, may be negative
  @return a {@code LocalDateTime} based on this date-time with the weeks added, not null
  @throws DateTimeException if the result exceeds the supported date range