App.xaml.cs

using System;
using System.Windows;
using System.Windows.Threading;

namespace WpfApp1
{
	/// <summary>
	/// Interaction logic for App.xaml
	/// </summary>
	public partial class App : Application
	{
		private readonly MainWindow _mainWindow;
		private readonly BookingWindows _bookingWindow;
		private readonly DispatcherTimer _dispatcherTimer;

		private readonly TimeSpan _start = new TimeSpan(7, 30, 0);
		private readonly TimeSpan _end = new TimeSpan(16, 30, 0);

		public App()
		{
			_mainWindow = new MainWindow();
			_mainWindow.WindowStartupLocation = WindowStartupLocation.CenterScreen;
			_mainWindow.SourceInitialized += (s, a) => _mainWindow.WindowState = WindowState.Maximized;

			_bookingWindow = new BookingWindows();
			_bookingWindow.WindowStartupLocation = WindowStartupLocation.CenterScreen;
			_bookingWindow.SourceInitialized += (s, a) => _bookingWindow.WindowState = WindowState.Maximized;

			_dispatcherTimer = new DispatcherTimer();
			_dispatcherTimer.Interval = TimeSpan.FromSeconds(1);
			_dispatcherTimer.Tick += _dispatcherTimer_Tick;

			_mainWindow.Closed += window_Closed;
			_bookingWindow.Closed += window_Closed;
		}

		private void window_Closed(object sender, EventArgs e)
		{
			Current.Shutdown();
		}

		private void _dispatcherTimer_Tick(object sender, EventArgs e)
		{
			var timeOfDay = DateTime.Now.TimeOfDay;

			if (timeOfDay >= _start && timeOfDay <= _end)
			//if (timeOfDay.Minutes % 2 == 0)
			{
				if (!_mainWindow.IsVisible)
				{
					_mainWindow.Show();
				}

				if (_bookingWindow.IsVisible)
				{
					_bookingWindow.Hide();
				}
			}
			else
			{
				if (!_bookingWindow.IsVisible)
				{
					_bookingWindow.Show();
				}

				if (_mainWindow.IsVisible)
				{
					_mainWindow.Hide();
				}
			}
		}

		private void Application_Startup(object sender, StartupEventArgs e)
		{
			_dispatcherTimer.Start();
		}
	}
}