Duration: P1Y2M3DT10H30M is 37017000 seconds Seconds: 37017000 is P1Y2M3DT10H30M duration Duration: -P120D is -10368000 seconds Seconds: -10368000 is -P4M duration Seconds: 1500798720 is P47Y7M5DT8H32M duration Duration: P47Y7M5DT8H32M is 1500798720 seconds Add should be PT0S: PT0S Subtract should be PT0S: PT0S