Sorry about that. When didn't the timestamps match the actual publication date? It'd be great if you could find when.
This extension works without requiring a Youtube API server by scraping the data so in the best case scenario it's just detecting something else as the date due to the data to scrape being undocumented, or in the worst case that data is used for something that doesn't require it to be accurate and so it isn't accurate.
Either way, I would like to see if I could do something about it.
The Github is linked in the description so you can contact me and post links & images there.