There is never a bad time to read the poetry of Mary Oliver, but Sunday afternoon seems like an especially good time. You may have some of her work already. If so, why not pull it down and savour it?
You may have a favourite outside of these. As for me, it has two of my favorites, Wild Geese and The Summer Day. Go and enjoy. Happy Sunday to you.
P.S. I wrote this on her as well. Some good links in that post.