I have done an answer in this question, but I wanted to see the exact hour I sent the answer, not 3 hours ago. I know that I can do it in the comments, but how can I do that in answers?
As explained in the comments, if you hover with the cursor over the text showing time (like "3 hours ago" or "yesterday"), a tooltip showing exact time will be shown. The same is true for many other timestamps in the Stack Exchange user interface. (And in general, tooltips are often used here as a way to provide some additional information. So hovering about something is worth trying if you are not sure what it means or what it is used for.)
I will also add screenshot taken from this meta.SE question: Should we see timestamp when an answer was appeared on?