So, I fat-fingered the 2016-05-18 entry, and, consequently entered the date incorrectly
Fortunately, the incorrect date, 2016-05-08, was a Sunday: a non-trade day, so there were no doubled-entries. Linkages were correct, so I simply corrected the node information, updated the database and voilà!
Now, if data were corrupted, I would have had to restored from the backup before the offending date 2016-05-08, but, since this was simply a mis-name and not a linkage issue, the in-place correction suffices.
p.s.: Now to correct the underlying conceptual graph.