Write a program that reads a string from the keyboard and tests whether it contains a valid date. Display the date and a message that indicates whether it is valid. If it is not valid, also display a message explaining why it is not valid. The input date will have the format mm/dd/. A valid month value mm must be from 1 to 12 (January is 1). The day value dd must be from 1 to a value that is appropriate for the given month. February has 28 days except for leap years when it has 29. A leap year is any year that is divisible by 4 but not divisible by 100 unless it is also divisible by 400.