To switch wallpaper images periodically or at exact time:
1. turn on autochanging wallpapers - check Enable autochanging of background images box in Background -> Changer;
2. select one of three switching options and set the time or period:

• Period - background will be changed with given time period. Select an appropriate time period for switching wallpapers from the drop-down menu. There are available periods from 5 minutes to 12 hours and, also, 1 month period to change backgrounds every month like a loose-leaf calendar.
• Days of week - background will be changed only on selected days of week. Default setting is every day (every weekday is checked). You can check\uncheck any day if you need.
• Exact time (every day) - background will be changed every day at given time. Set time and click "+" button to add the time to the time list. You can add as many time points as you want. You can delete time from the list using "-" button. Also, you can simply uncheck unneeded time instead of deleting it from the list, and check it later when you need it again.
   

Check Every start up option to change the background at every Windows startup.

Change only if Screen Calendar is minimized option doesn't allow the program to change pictures till you finish the setup.

Also, you can see different wallpaper every time you click Change now button. It is a very easy way to choose new desktop wallpaper and it doesn't depend on whether the Enable autochanging of background images option is active or not.

To enable auto-changing, you should select a folder or an image list as a background image source in Background.

When background changer is turned on, it's recommended to use Chameleon skin to see a contrast calendar over any wallpaper. See Skins and Chameleon settings for details.