Event date range not reflecting corrected clip dates

When we hover the cursor over an event title, it shows the range of dates for the clips inside; And if we change the dates of the clips, the event date range should change too, right?

I corrected the dates (year) for ALL clips in four different events using the >Modify >Adjust Clip Date and Time --keeping checked "Change file creation dates as well."

ONE of the four events moved to the correct new year (my events are sorted by year); the other three did not. When i hover over the event titles, I see that the date ranges now go from the NEW date to the OLD date. But there are no longer any clips with the old date! I went back to >Modify >Change Date and Time for EACH ONE individually to confirm that they all show the correct new date.

(and yes, i did set the event browser to show "All clips" so there were no rejected clips hiding out of view.)

Can anonyone suggest why an event would hold an old date in the range when there are no longer any clips with that date?

I've closed and reopened the library; i even closed and reopened iMovie. I'm out of ideas.

Thanks!