Mid 1980's.
1976
198x.
No Model 36 (marked as such) had that serial number. The Chief Special which later became the Model 36 with that serial number was made in the early 1950's, before S&W assigned model numbers. The serial number on your gun is located on the butt.
1975-1976
c.1971
If the serial number is J75635 then your Smith and Wesson model 36,J frame revolver was made between 1979-1980.
@1977
c.1956
@ 31 yrs old
Made in 1981.
Early to mid 80s
@ 30 years old