Duration: P1Y2M3DT10H30M is 37017000 seconds Seconds: 37017000 is P1Y2M3DT10H30M duration Duration: -P120D is -10368000 seconds Seconds: -10368000 is -P4M duration Seconds: 1560959635 is P49Y6M1DT15H53M55S duration Duration: P49Y6M1DT15H53M55S is 1560959635 seconds Add should be PT0S: PT0S Subtract should be PT0S: PT0S