Find file creation date

To find when a file was first tracked, git log can be used:

$ git log --format=%aI --follow -- README.md | tail -1
2020-04-18T20:37:08+02:00

Do this in a for-loop, and you get a history of when all TILs in this repo were created:

for file in $(ls **/*.md); do
    echo "$(git log --format=%aI --follow -- $file | tail -1): $file"
done

See man git log for more date formats.