C#

private static double CalculateDifferance(object from, object to)
{
   Type t = typeof(from);
   // are you confident that both types match?
   // if(!(to is t))
   //   throw new InvalidOperationException("from and to must be of the same type!");

   switch (t)
   {
      case System.Int32:
         return (int)to - (int)from;
         break;
      case System.DateTime:
         return ((DateTime)to  - (DateTime)from).TotalSeconds;
         break;
      case System.Double:
         return (double)to  - (double)from;
         break;
      default:
         return double.NaN;
         break;
   }
}

public static double CalculateDifference(double to, double from){
    return to-from;
}
public static int CalculateDifference(int to, int from){
    return to - from;
}

public interface IMath<T>
{
    double CalculateDifference(T from, T to);
}
public class TestMath : IMath<int>, IMath<double>, IMath<datetime>
{
    #region IMath<int> Members

    public double CalculateDifference(int from, int to)
    {
        return to - from;
    }

    #endregion

    #region IMath<double> Members

    public double CalculateDifference(double from, double to)
    {
        return to - from;
    }

    #endregion

    #region IMath<datetime> Members

    public double CalculateDifference(DateTime from, DateTime to)
    {
        return (to - from).TotalSeconds;
    }

    #endregion
}

TestMath testMath = new TestMath();
Console.WriteLine(testMath.CalculateDifference(DateTime.Now, DateTime.Now.AddDays(1)));