[no_one_ever]

Rather than 'up and down', I think the visual is supposed to be 'up and back' (like forward and backward).

English is fun

[quietbritishjim]

More usually (in the UK) it's forward and back, which make more sense as direct opposites. It's a little confusing though because pushing something back means move it later and bring it forward means move it earlier, whereas when talking directly about time the meanings are usually reversed (e.g. "back in time" means earlier).

[uryga]

in this case i'd interpret "forward/backward" as "closer towards you / further away from you", with the metaphor being that you're standing on a timeline looking "in the future direction" and moving stuff closer/further.

when using "back" to talk about the past, it's "backwards" as in "behind you". "further back" = "further behind you" = "more in the past"

[kbutler]

Does "back in time" mean earlier when speaking of future events? Or only past events?

A future meeting "moved back" is definitely postponed. (US English)

[slver]

And yet when you "set something back" you move it later in time.