code: public Period minusDays(long daysToSubtract) {
          return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
      }
docs: Returns a copy of this period with the specified days subtracted.
  <p>
  This subtracts the amount from the days unit in a copy of this period.
  The years and months units are unaffected.
  For example, "1 year, 6 months and 3 days" minus 2 days returns "1 year, 6 months and 1 day".
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param daysToSubtract  the months to subtract, positive or negative
  @return a {@code Period} based on this period with the specified days subtracted, not null
  @throws ArithmeticException if numeric overflow occurs