There's one information by Kinbote where he specifies that an event "pratically coincided" with another one. There's a big margin for speculation after this additional "pratically." However, it is possible to surmize that Shade's heart attack (in October 17,1958) took place one or two days before King Charles's spectacular invasion of a hay field in America. 

 

Kinbote writes his last lines in October, 19, 1959.  It is highly probable that his parachuting down near Baltimore took place also in October 19, 1958..

He provides the date of John Shade's illness about which he learned on the day of his arrival in America, but through a newspaper article that had been underlined by Sylvia. One cannot exclude the fact that his descent may have taken place in October 18 but, for symmetrical reasons, I think that Kinbote chose to stage his disappearance for October 19, on the first anniversary of his surfacing in America. .  .   

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CK's last lines: "To this statement my dear poet would probably not have subscribed, but, for better or worse, it is the commentator who has the last word.
Charles Kinbote
Oct. 19, 1959, Cedarn, Utana"

The  arrival of King Charles: "John Shade’s heart attack (Oct. 17, 1958) practically coincided with the disguised king’s arrival in America where he descended by parachute from a chartered plane piloted by Colonel Montacute, in a field of hay-feverish, rank-flowering weeds, near Baltimore "

Although this coincidence must have been pointed out already, I think that it may interest as a reminder to those List members who are intent on birthdays and anniversaries.

From internet timelines I extracted the following information:" October 19, 1951: President Truman signs an act formally ending World War II."