UPDATED: New Last Played Date v4.0
New Last Played Date v4.0 will set the Last Played/Last Skipped date of selected tracks to a new user-entered date, with an option to increase or decrease Plays/Skips, or set tracks to no date and no Plays/Skips (effectively making them never played).
This latest version has support for OS X 10.10 Yosemite and iTunes 12, adds a "Check for Update" command, and makes a few minor UI and performance tweaks.
More information and download is here.