Write a Python program that takes two times in military format $($e$.$g$.,0900,1730)$ as input and calculates the time difference in hours and minutes between them. Consider the following constraints:

Implement input validation to ensure that the user enters valid military time formats.

Handle cases where the second time is on the next day, and the time difference spans across midnight.

Your program should:

Prompt the user to input the first time, ensuring it is a valid military time format.

Prompt the user to input the second time, ensuring it is a valid military time format.

Calculate and display the time difference in hours and minutes, considering the additional constraints.

Ensure that your program provides accurate and meaningful results in all possible cases.