Hindsight means the opportunity to judge or understand past events using
knowledge that you have gained since then. The 20/20 indicates vision
sharpness or clarity. This proverb refers to retrospection. You may not always
have ‘the clearest vision’ when you are making a decision, but given a little
more time, your ‘vision’ seems too clear. That’s why anything in hindsight
(retrospection) is always seen more clearly with 20-20 vision. This proverb is
also used in an ironic way to mean: ‘It is easy to be wise after the event.‘