test/hour_arithmetic.exp

   1 14:22:45 + 11:45:30 = 26:08:15
   2 14:22:45 += 11:45:30 = 26:08:15
   3 11:05:30 - 01:20:40 = 09:44:50
   4 11:05:30 -= 01:20:40 = 09:44:50
   5 22:59:59++ = 23:00:00
   6 ++22:59:59 = 23:00:00
   7 22:00:00-- = 21:59:59
   8 --22:00:00 = 21:59:59
   9 PASS hour_arithmetic (exit status: 0)