tag ls: "last pushed" and "last update" columns are confusing

[thaJeztah]

Description

I got a bit confused about the meaning of both columns (LAST UPDATE and LAST PUSHED);

• what's the difference between these?
• can they be different? (e.g. a push without updating the image?)
• if so; does a push without updating reset the STATUS (stale -> active)?
• Do we support a push without updating?
• Should we remove one?

I also noticed that the output format is inconsistent ("3 weeks ago" vs "3 weeks");

TAG                           DIGEST                                                                     STATUS    LAST UPDATE      LAST PUSHED    LAST PULLED       SIZE
nginx:latest                  sha256:f19d295b57fdde6f71573f487b35875ca95bd23401b142eb55eeb9d887f9f5b1    active    3 weeks ago      3 weeks        10 minutes        421.2MB
nginx:stable-alpine-perl      sha256:0c85226446a083d92fbf432faee51d12933eafdcf13eb0b7d06fc465368ae908    active    2 weeks ago      2 weeks        12 minutes        124.8MB
nginx:stable-alpine           sha256:da3716611fb965f3fda1f3281882baeb2760ca8bb7317f1d22ed45e75570827b    active    2 weeks ago      2 weeks        32 seconds        64.99MB

Output of docker hub --version:

Docker Hub Tool v0.2.0, build 0edf43a