On Tuesday, July 12, 2011, the planet Neptune completes its first revolution around the sun since its discovery on September 23, 1846. Neptune finally reaches this milestone at 22:27 Universal Time today. It takes Neptune 164.79 Earth-years to go full circle through the constellations of the Zodiac, whereas the Earth goes full circle in just 365.256 days.
http://earthsky.org/tonight/neptune-...n-july-12-2011

The article says you need high-powered binoculars or a telescope to see it if you feel like planet watching on July 12.