The top hit, however, was a fresh Reddit thread with Alexa users reporting the same issue. After keeping an eye on it, I saw a user come up with the solution that worked for me (and it is the only solution on the thread so far).
Launch the Alex app and go to Settings, select a device, and change the timezone
- from America/Eastern Standard Time
- to US/Eastern Standard Time
The fix takes immediately: just ask “Alexa, what time is it?” — no power cycling needed.