Relative dates are one of the worst examples of overengineering we find nowadays: makes it more difficult to know the exact date (which month? which day of week? which time of day?), to know which date is earlier or later ("4 days ago" vs "4 days ago"), rounding problems, does not work if you print the date or take a screenshot, ... so many issues that even having the option to hover over the date is not enough to fix the problem.
Since those websites usually provide the absolute date if you hover the mouse over the relative date, the data must be there somewhere and it is probably possible to create a user script or browser extension that replaces one value with the other.
Is there anything like this for Chrome or Firefox?