Scanned photos all show up on the day you scan them. Timeline Scan estimates when each photo was actually taken and writes it into the file’s EXIF, so your archive sorts chronologically in Immich, Google Photos, or Apple Photos (or by folders if you’re one of those people). I increased the trial to 50 photos; try it out and let me know what you think!
It does both. Each image and then neighbors. Usually you scan photos that are printed in related-date order. So it does look at neighboring photos to date.
You can tag faces and add a birthdate; so sort of. Like it'll recognize a birthday party photo and then if it's tagged with that person in the picture, it will date it on their birthday.
