In their article “My Mother, Whenever She passed Away, She Had Pneumonia: The History and Functions of whenever,” Michael Montgomery and John Kirk discuss the “punctual” whenever, a vestige of Scots-Irish usage heard in much...
Some speakers of American English use the word whenever to refer to a single event, as in “whenever Abraham Lincoln died.” This locution is a vestige of Scots-Irish speech. This is part of a complete episode.