code: public Duration minusDays(long daysToSubtract) {
          return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
      }
docs: Returns a copy of this duration with the specified duration in standard 24 hour days subtracted.
  <p>
  The number of days is multiplied by 86400 to obtain the number of seconds to subtract.
  This is based on the standard definition of a day as 24 hours.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param daysToSubtract  the days to subtract, positive or negative
  @return a {@code Duration} based on this duration with the specified days subtracted, not null
  @throws ArithmeticException if numeric overflow occurs