Integer to Time Conversion

[C# Programming]

I need in a console application to have user input an integer in military time that be converted some how to 13:00 or 13:30 instead of 1330 the pure number. So that I can then take 1330 and have the user input an end time like 1430 and increase it by 25 percent to come out with 1445 or 2:45. So your increases the total time from 1 hour to 1 hour and 15 minutes. The input will always be HHMM in military time
Simple Function is needed nothing advanced