### Changing an ITime Object

You can add or subtract two times. Four operators are provided: +, +=, -, and -=. The following example shows the use of these operators:

    ITime Start(12:00), Duration(2:00),
          Done=Start+Duration;           // Done=14:00
    Start=Done-Duration;                 // Start=12:00 still
    Start+=Duration;                     // Start=14:00
    Start-=Duration;                     // Start=12:00 again