This discussion may contain spoilers!
I just realized that when Doc explains to Marty where the car came from, he says it was sent 70 years into the future, to 2025. However, upon closer inspection to the time circuits, Doc actually landed at midnight on January 1, 1885 (AM and PM appear to be switched, at least in Part II).
The amount of time between these days is about 70 years, 10 months, 20 days.
However, that much time after November 21, 1955 would actually fall into 2026.