Why Are My Photos Off by One Day?
A time zone conversion shifted a photo taken near midnight across the date line into the day before or after.
A photo taken at half past eleven at night is only thirty minutes from the next day. Convert its time into a different zone and it crosses over. Nothing is broken; the moment is right and the label moved.
It shows up most after travel, or when a library is processed on a computer set to a different zone from the one the photos were taken in.
Takeout JSON Metadata Fixer converts carefully rather than assuming your current zone, which keeps late-night photos on the day they happened. It runs on your own computer and is free for your first 500 photos.