To fix a Flickr export free: drop a zip holding your photos and their photo_*.json files anywhere on this page. Your browser matches each JSON to its photo by Flickr's photo ID and writes the real date taken back into the EXIF. No upload, no file cap, no signup.
How to prep your export (one minute)
Flickr gives you several "data" zips (the JSON) and several photo
zips. Unzip them into one folder so the photo_12345.json
files sit alongside the images, then use "pick an unzipped export folder"
above, or re-zip that combined folder and drop it. Matching runs on the
photo ID Flickr embeds in both filenames, so album structure doesn't
matter.
FAQ
What gets restored?
Date taken goes into each JPG's EXIF (where every photo app reads it) and file timestamps are corrected for everything else. Titles/tags/albums restoration is on the workbench.
Why did Flickr do this?
Their export pipeline separates "your content" from "your data" for compliance reasons. Fine for lawyers, useless for your photo library.
Uploaded anywhere?
No. Matching and EXIF writing run in your browser. Decades of photos stay yours alone.