In "The Picnic"
Eventually, once everything was done and Hater had made his wish, the planets presumably returned to their original position.
The location of the planetary alignment was in the planet where the temple was located, and the date is currently unknown. The alignment happens once every millenium, as stated by Hater.
In "The Time Bomb"
The planetary alignment played a small, but key role in the episode, since it made possible the race track for the Galactic Conjunction 6000. The alignment happens once a year.