Time::operator-=

Design the subtraction in theTimeas if you are turning a 24-hour clock backwards:

Time& operator-= (const Time& D); 

Calculates the time difference between the current time and the incoming argument TimeDand the returns the reference of the left operand object. Note that the difference can never be a negative value:

23:00 -= 9:00 will be14:00.

18:00 -= 16:00 will be2:00.

1:00 -= 22:00 will be3:00. ((1:00+ 24:00) -22:00)

Also:

1:00 -= 46:00 will be3:00. ((1:00+ 24:00 + 24:00) -46:00)