Would this work?

if (DateTime.Now.DayOfWeek == DayOfWeek.Saturday && DateTime.Now.Hour == 8)
                                    {
                                        World.GWOn = true;
                                        World.SendMsgToAll("Guildwar has started!", "SYSTEM", 2000);
                                        World.SendMsgToAll("Guildwar has started!", "SYSTEM", 2011);
                                    }
                                    if (DateTime.Now.DayOfWeek == DayOfWeek.Sunday && DateTime.Now.Hour == 23)
                                    {
                                        World.GWOn = false;
                                        World.SendMsgToAll("Guildwar has ended!", "SYSTEM", 2011);
                                        World.SendMsgToAll("Guildwar has ended!", "SYSTEM", 2000);
                                    }