Spotify's Autoplay feature is phenomenal. Sometimes it hits you out of the blue with the most incredible afternoon of music - it's almost like it's adopted a DJ persona that fits perfectly with your current music needs. The problem (first world) is that it's devastagingly ephemeral.
It would be amazing if I could save Spotify's DJ "brain state" (whatever mood it seems to have adopted) as a dynamic playlist of some kind. As in, whatever the **bleep** it was doing yesterday afternoon from 13:00 to 21:00 - I want to be able to ask to do it again.