using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var dates = new List<DateTime>() { DateTime.Parse("1980-01-01"), DateTime.Parse("1990-01-01"), DateTime.Parse("2030-01-01") };

        var pastDates = dates.Where(x => x.CompareTo(DateTime.Now) < 0);

        foreach(var date in pastDates)

        {

            Console.WriteLine(date);

        }

    }

}

​