Especially because it becomes so imprecise.
On YouTube, "1 year ago" can mean anywhere from 365 to 729 days. Anything between 1 and 2 years ago becomes "1 year ago".
So if I see two videos that were both uploaded "a year ago", it's impossible to know which is more recent without actually opening the videos, going to the description, and looking at the date.
So if I see two videos that were both uploaded "a year ago", it's impossible to know which is more recent without actually opening the videos, going to the description, and looking at the date.