There are utilities which can show you the "last modified date" of a key.
(For a solution for changing the timestamp look at the bottom of this answer.)
Even with "regedit.exe" you can determining the "Last Write Time" of a registry key:
Run and type
- Navigate to the key for which you want to determine the last write time
- From the
File menu, click
- In the
Save As type drop-down box, select
Text Files (*.txt)
- Type a file name and press Enter
- Open the text file using Notepad, and look at the
Last Write Time value.
Key Name: HKEY_USERS\.DEFAULT\Control Panel\Desktop
Class Name: <NO CLASS>
Last Write Time: 3/5/2006 - 11:45 AM
You can find these instructions on this site here.
There it says you can also use the Regscanner from Nirsoft.
Here is also a good article about A Forensic Analysis Of The Windows Registry.
If you want to change these timestamps you could look at the utility SetRegTime.