This is more of an information than a solution.
If you view the previous versions under Properties of a Network folder, you may find all the versions have the same day of the folder creation than the backup version for the folder. The same folder will show the appropriate dates when viewed from a Windows Vista or a Windows XP machine.
Don’t worry, you are not alone. This is a known bug in Windows 7 with the Volume Shadow copy and is being worked at. Lets hope this bug is fixed sooner.