I have arduino mega 2560 and i want to make a countdown. But i want to type with membran keypad a hour and with this hour and with actual hour create a countdown on a lcd display. Example : i type 8:00 am and actual hour its 7:00 am, i have a 1:00 hour countdown.

I dont have idea how to make that.

Ty have a nice day.

You get a keypad and wire it up to your mega. You upload some of the examples to make sure it works and you understand it.

You do the same with an lcd display.

You combine the two sketches into one and get that working.

If/When you have problems, you post your code here, along with the problem and people will help you.

by the way, how will your mega know that it is 7am? It does not have a real-time clock. You may need one of those as well.