Can I Fix Photo Dates on My Phone?
Phone apps can edit a date, but a large library needs a computer. Here is why.
Both platforms can change one photo's date. iOS Photos has an Adjust Date and Time option. Android gallery apps often expose a similar edit. Fine for a handful of pictures.
A Google Takeout export is a different problem. It arrives as large zip files full of .json sidecars, and phones are poor at unzipping many gigabytes and have no tool that reads those sidecars in bulk.
Do the export and the fixing on a computer, then copy the corrected photos to your phone. They arrive with the right dates already inside them. Takeout JSON Metadata Fixer runs on Windows, Mac and Linux.