using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var start = "03/01/2020";

        var end = DateTime.UtcNow;

        var payperiods = MonthlyBuilder(DateTime.Parse(start), end);

        foreach (var payperiod in payperiods)

        {

            Console.WriteLine("\n");

            Console.WriteLine("PayPeriodStart: " + payperiod.PayPeriodStart.ToString());

            Console.WriteLine("PayPeriodEnd: " + payperiod.PayPeriodEnd.ToString());

            Console.WriteLine("PayDate: " + payperiod.PayDate.ToString());

            Console.WriteLine("\n");

        }

    }

​

    public static List<PayPeriodDates> MonthlyBuilder(DateTime startDate, DateTime endDate)

    {

        // payday should be the first day of the new pay period

        var payDates = new List<PayPeriodDates>();

        var candidateStart = startDate;

        while (candidateStart <= endDate)

        {

            var dates = new PayPeriodDates();

            dates.PayPeriodStart = candidateStart;

            while (candidateStart.Day != 1)

            {

                candidateStart = candidateStart.AddDays(1);

            }

            var candidateEnd = candidateStart.AddMonths(1).AddDays(-1);

            dates.PayPeriodEnd = candidateEnd <= endDate ? candidateEnd : endDate;

            dates.PayDate = candidateStart.AddMonths(1) >= endDate ? endDate : candidateStart.AddMonths(1);

                payDates.Add(dates);

            candidateStart = candidateStart.AddMonths(1);

        }

​

        return payDates;

    }

}

​

public class PayPeriodDates

{

    public DateTime PayPeriodStart { get; set; }

​

    public DateTime PayPeriodEnd { get; set; }

​

    public DateTime PayDate { get; set; }

}