public static DateTime When;
        private Timer OpTimer;

        protected void Application_Start(object sender, EventArgs e)
        {
            When = DateTime.Parse("00:00");
            StartTimer();
        }

        protected void StartTimer()
        {
            if (When < DateTime.Now)
            {
                while (When <= DateTime.Now)
                {
                    When = When.AddHours(1);
                }
            }
            OpTimer = new Timer(GetInterval());
            OpTimer.AutoReset = false;
            OpTimer.Elapsed += new ElapsedEventHandler(OpTimer_Elapsed);
            OpTimer.Enabled = true;
        }

        protected void OpTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            backup Backup = new backup();
            Backup.EseguiBackup();
            When = When.AddHours(1);
            OpTimer.Interval = GetInterval();
            OpTimer.Start();
        }

        protected double GetInterval()
        {
            TimeSpan diff = When.Subtract(DateTime.Now);
            return diff.Ticks / 10000;
        }