You can use it here: https://addons.mozilla.org/en-US/firefox/addon/youtube-times/
For each video, it takes the URL and fetches the video's page before scraping the exact time of upload.
It doesn't use the Youtube API so that I could avoid having to implement it in a way that would either require a proxy, OAuth validation that could deter users, or publicly revealing a Youtube API Token key as well as not have to worry about any usage limits.