How to Define your Work Week in the Regional Settings using CSOM in SharePoint 2013 Online

Code Snippet: 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Security;
using System.Text;
using System.Threading.Tasks;
using Microsoft.SharePoint.Client;

namespace CSOMOffice365
{
    class Program
    {
        static void Main(string[] args)
        {

            string userName = "[email protected]";

            Console.WriteLine("Enter your password.");
            SecureString password = GetPassword();

            // ClienContext - Get the context for the SharePoint Online Site
            // SharePoint site URL - https://c986.sharepoint.com

            using (var clientContext = new ClientContext("https://c986.sharepoint.com"))
            {
                // SharePoint Online Credentials
                clientContext.Credentials = new SharePointOnlineCredentials(userName, password);

                // Get the SharePoint web
                Web web = clientContext.Web;

                // Regional Settings
                RegionalSettings regSet = web.RegionalSettings;
                // Work days: https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.client.regionalsettings.workdays.aspx
                // Convert the binary value to decimal: 0110110  - 54
                regSet.WorkDays = 54;
                // First Day of Week: https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.client.regionalsettings.firstdayofweek.aspx
                regSet.FirstDayOfWeek = 1;
                // First Week of Year: https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.client.regionalsettings.firstweekofyear.aspx
                regSet.FirstWeekOfYear = 1;
                // Work Day Start Hour - https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.client.regionalsettings.workdaystarthour.aspx
                regSet.WorkDayStartHour = 540;
                // Work Day End Hour - https://msdn.microsoft.com/en-us/library/microsoft.sharepoint.client.regionalsettings.workdayendhour.aspx
                regSet.WorkDayEndHour = 1020;

                // Update the regional Settings
                regSet.Update();

                // Execute the query to the server
                clientContext.ExecuteQuery();
            }
        }

        private static SecureString GetPassword()
        {
            ConsoleKeyInfo info;

            //Get the user's password as a SecureString
            SecureString securePassword = new SecureString();
            do
            {
                info = Console.ReadKey(true);
                if (info.Key != ConsoleKey.Enter)
                {
                    securePassword.AppendChar(info.KeyChar);
                }
            }
            while (info.Key != ConsoleKey.Enter);
            return securePassword;
        }
    }
}

Output