What Time Zone Do Takeout Dates Use?
The .json files store the moment in UTC. Whether you see the local time depends on the tool that reads them.
Google stores the time as a number of seconds since 1970, which is a UTC moment with no time zone attached. It is exact, but it does not say what the clock on the wall read where the photo was taken.
A tool that converts that number using your computer's current zone can shift a photo by hours, and a photo taken near midnight then lands on the wrong day.
Takeout JSON Metadata Fixer handles the conversion carefully and can use the photo's own time zone when it has one. It runs on your own computer and is free for your first 500 photos.