using System;

using AutoMapper;

​

public class Program

{

    public static bool FilterBills(Bill bill)

        {

​

            //threshold days

            const int THRESHOLD_DAYS = 6;

​

            if (bill.BillDebitDate==null)

            {

                return false;

            }

            //valid dates

            var validDate = bill.BillDebitDate != null && bill.BillDebitDate.HasValue && bill.BillDebitDate.Value.Date.AddDays(+3) >= DateTime.Now.ToUniversalTime().Date;

​

            //check its within the threshold

            var dayDifference = (bill.BillDebitDate.Value.Date.AddDays(+3) - DateTime.Now.ToUniversalTime().Date).TotalDays;

            var validThreshold =  dayDifference <= THRESHOLD_DAYS && dayDifference >= 0;

            Console.WriteLine(bill.BillDebitDate.Value.Date+" Adding 3 days " + bill.BillDebitDate.Value.Date.AddDays(+3)+" "+validDate +" "+dayDifference+" "+validThreshold + " Result "+(validDate && validThreshold) +" After Condition " 

                              + (bill.BillDebitDate.HasValue && bill.BillDebitDate.Value.Date.AddDays(-3) < DateTime.Now.ToUniversalTime().Date ? "Late":"Upcoming"));

            return validDate && validThreshold;

        }

    public static void Main()

    {

        Bill M4Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date.AddDays(-4)};

        FilterBills(M4Todaybill);

        Bill M3Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date.AddDays(-3)};

        FilterBills(M3Todaybill);

        Bill M2Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date.AddDays(-2)};

        FilterBills(M2Todaybill);

        Bill Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date};

        FilterBills(Todaybill);

        Bill P3Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date.AddDays(3)};

        FilterBills(P3Todaybill);

        Bill P4Todaybill = new Bill() {BillDebitDate = DateTime.Now.ToUniversalTime().Date.AddDays(4)};

        FilterBills(P4Todaybill);

    }

}

​

public class Bill

{

    public DateTime? BillDebitDate { get; set; }    

}