SKTimeStamp is a free software which gives you the power to change the creation date / last modified date / last accessed date of a specified file. It is a simple to use tool and is integrated with Windows Explorer, SKTimeStamp works on both Windows 7 and Windows XP, and has both 32bit and 64bit versions.
If you want to fool your boss / coworker / husband / wife and make they think that you launched something on someday, you can use SKTimeStamp to get things done easily and efficiency.
To use SKTimeStamp, just download and install it, then right click on a file, navigate to the TimeStamps tab, then you can change the date and time to anything.
SKTimeStamp is available as a free download from Google code.