alright, here is a picture of what i believe is the oldest LD with Widescreen.

as you can see in the picture i posted it has a date of 1982. that pretty much sums it up, pioneer was the first to release widescreen for home first.

Pied Piper, The (1972) [FY026-26VC]

I know the database street date stuff isn't comprehensive, but Halloween (1978) [K88L-5036] has a street date of 1981 and shows as being widescreen. thats the only one the database came back with prior to '82 and being widescreen. i don't have the title so idk how accurate it is.

The oldest I have Close Encounters of the Third Kind: Special Edition #125 (1980) [CC1241L] from 1990....not that impressive really.

In my collection, probably Terror in the Aisles: That's Shock.

The first LaserDisc of Halloween was by Media on Image in 1985 as an awful P/S transfer. The first widescreen was the Criterion CAV edition.

I think it probably correct.
LD the first in Japan since October 1981.

Of course, I also own a copy.
I bought it new in more than 20 years ago.