Duration: P1Y2M3DT10H30M is 37017000 seconds Seconds: 37017000 is P1Y2M3DT10H30M duration Duration: -P120D is -10368000 seconds Seconds: -10368000 is -P4M duration Seconds: 1496128171 is P47Y5M11DT7H9M31S duration Duration: P47Y5M11DT7H9M31S is 1496128171 seconds Add should be PT0S: PT0S Subtract should be PT0S: PT0S