- (((16:30 - 08:00) - PT1H) - (15 * PT1M))
(((16:30 + (-1 * 08:00)) - PT1H) - (15 * PT1M))
(((16:30 + PT-8H) - PT1H) - (15 * PT1M))
((PT8H30M - PT1H) - (15 * PT1M))
((PT8H30M + (-1 * PT1H)) - (15 * PT1M))
((PT8H30M + PT-1H) - (15 * PT1M))
(PT7H30M - (15 * PT1M))
(PT7H30M - PT15M)
(PT7H30M + (-1 * PT15M))
(PT7H30M + PT-15M) = PT7H15M
!?