Just found this while tinkering. If anyone else could test, I'd appreciate it.

Steps to recreate: 

1. Add record via form in interfaces
2. Make sure the form submission has a datetime field, and set that field's default value to Current Time.
3. Toggle off 'Allow users to edit this field'.
4. Submit form

When the record is created, the date field will have 24 hours added to it.

I originally thought it had something to do with my timezone settings and GMT, but when I toggle on 'Allow users to edit this field', the 24 hours is not added to the date field on record creation.

I have a video here that shows it happening to me.