This episode was produced in 1983 and was originally planned to air in the second season (production number 035), but for some reason, NBC refused to air it until 1987.
The title is from the song "The Anniversary Waltz" written by Dave Franklin, the lyrics by Al Dubin and published in 1941.
If it seems rather odd that after the kids have grown and matured over the course of 6 years at this point in the series,only for them all to be much younger again like they were in the early seasons,and even the adults to appear a little younger again as well in this episode,this is because this show was produced 4 years earlier for season 2! But for unspecified reasons NBC didn't air it until midway through season 6. While the show would return to present day after this it would go back in time again,back to season 2,for another episode produced for said season,"Return Of The Native",later on towards the end of this season.