KMail message listing oddity at midnight

[KMail 5.7.3 on Fedora 28]

I leave KMail open on the last message in my Inbox, with the last message 
highlighted in the Message List and the message open in the Message Pane.

At midnight, the message listing dividers change, e.g., the last one changes 
from "Today" to "Yesterday".

When that happens, the Message List changes to highlight the 2nd-last message, 
and the Message Pane shows that message.

Then I go to my kdepim-users folder to open a message to the list.

When I go back to my Inbox it shows the (proper) last message.

Something in the date rollover is slightly off.