Effective Solution

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter takeoff hour: ");
            int hour = int.Parse(Console.ReadLine());
            Console.Write("Enter takeoff mins: ");
            int min = int.Parse(Console.ReadLine());
            if (hour < 7)
            {
                if (min != 0)
                    min = 60 - min;
                if (min == 0)
                    hour--;
                hour = 6 - hour;
                //DateTime takeoff = new DateTime(1, 1, 1, hour, min, 1);
                //Console.WriteLine("Can only take off in " + takeoff.ToString("hh:mm"));
                Console.WriteLine("Can only take off in " + hour + " hours and " + min + " minutes.");
            }
            else
                Console.WriteLine("Takeoff is green lighted");

        }
    }
}