The previous milestone on Viktor Korchnoi's Tournament, Match, and Exhibition Record (TMER; 1946-2015) was Korchnoi's Career 1976-2000, One View, where at the end I noted the next step:-
Assign months to the various events. At the same time, create a list of external references for the events.
I started to look up events one by one, noting the month the event was played and the best reference I could find. This was a slow process until I found Chessmetrics Player Profile: Viktor Korchnoi. The page is a summary of the major events in Korchnoi's career that were played at slow time controls. Some older events are missing the month played, but I was able to cover around 75% of the events already listed on the TMER.
Next step: (1) Tackle the incomplete events for 1976-2000. (2) Use the Chessmetrics.com data on events played before 1976.