Modfifying ToString() and Passing values from struct to Main Method()

In the following code, I am trying to change it to declare a read-only property Hour returning the number of hours and a read-only property Minute returning the number of minutes. For instance, new Time(23, 45).Minute should be 45. I need to modify the ToString() method so that it shows a Time in the format hh:mm, for instance 10:05, instead of 605. How can I use String.Format to do the formatting in the Main() Method?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Timers;
namespace TestTime
{
class Program
{
static void Main(string[] args)
{

Time timenow = new Time(1,2);

Console.WriteLine("Time={0} ", timenow);
Console.WriteLine("Press Any Key");
Console.ReadKey();

}
public struct Time
{
public readonly int minutes;

public Time(int hh, int mm)
{
Console.WriteLine("Enter Hour");
hh = Int32.Parse( Console.ReadLine());
Console.WriteLine("Enter Min");
mm = Int32.Parse( Console.ReadLine());

this.minutes = 60 * hh + mm;
}
public override String ToString()
{
return minutes.ToString();
}

}
}
}