using System;

public class Program

{

    public static void Main()

    {

        DateTime sourceFrom = new DateTime(2021,05,31);

        DateTime sourceTo = new DateTime(2021,06,11);

​

        DateTime targetFrom = new DateTime(2021,05,20);

        DateTime targetTo = new DateTime(2021,05,31);

        Console.WriteLine($"Overlap? {sourceFrom < targetTo && targetFrom < sourceTo}");

    }

}