In Windows 7, adding the Calendar Gadget is very simple as adding other Gadgets. Just right click on your desktop select Gadgets and drop and drop the Calendar Gadget to your desktop. Now you can see the Calendar showing the current date.
When you want to see all the dates for this month, previous or future, just double click the Calendar Gadget. This will show you the full Calendar for this month. You can use the arrow keys at the top which will navigate to other months.
To get back to its normal view double click on the current date. This is very simple for viewing the Calendar.