using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        static IEnumerable<(DateTime MinDate, DateTime MaxDate)> GetDateRange(DateTime minDate, DateTime maxDate, int daysChunkSize)

        {

            DateTime markerDate;

​

            while ((markerDate = minDate.AddDays(daysChunkSize)) < maxDate)

            {

                yield return (MinDate: minDate, MaxDate: maxDate);

                minDate = markerDate;

            }

        }

        string minInput = "2020-03-18 07:00:00.0000000";

        string maxInput = "2020-03-20 15:00:00.0000000";

        DateTime minDate = DateTime.Parse(minInput);

        DateTime maxDate = DateTime.Parse(maxInput);

        var foo = GetDateRange(minDate, maxDate, 1);

        foreach (var bar in foo)

        {

            Console.WriteLine($"{bar.MinDate}, {bar.MaxDate}");

        }

    }

}