The year on which you have passed all your examination is the year of graduation. As you have passed all your papers on 2020 then you have passed out on 2020. As a result, I would recommend you to use 2020 as the year of passing out.
I hope this answer helps. All the very best for your future endeavors!
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile