We can check by re-clicking on a vote to see the exact vote time as shown in this image. Actually it's not a feature, but a side effect of voting on a post that has already been locked. :-)
However, if the post is edited after the vote, then it will simply get unvoted. Neither the hovering of mouse nor the
timeline shows the date-time.
Is there a standard way which allows us to see the vote timing for a question or an answer?