Hi Tim,
Thanks for reaching out, and I’m sorry you’re running into this issue – you are correct that the events should not be disappearing the day before.
Can you go under Settings > General and verify that the timezone setting is correct? If this is off, that could be the reason they are disappearing early.
If this is still occurring with the correct timezone, can you try upgrading to the latest versions of The Events Calendar (4.5.8) and Events Calendar Pro (4.4.14)?
Finally, testing for conflicts with your theme and other plugins would be the next step in determining the source of the issue.
Let me know how it goes!
Thanks,
Jennifer