Well the 2016 calendar is still advertised on the home page so by that yard stick planetary oppositions still have 4 years to run. In the meantime try
https://www.planetary.org/articles/0...njunctions-rpx
There are many other resources online including U.S. Naval Observatory but that site appears to be under maintenance from a couple of years ago. Perhaps the whole internet is regressing or moving so fast that time has slowed.
See
https://www.usno.navy.mil/USNO
And
https://www.usno.navy.mil/USNO/astro...l-applications