I arrived a year ago. (Time↝Interval) [points backwards from the present: before now] Interval#001

I arrived a year back. (Time↝Interval) Interval#002

The game started at 7:00, but I arrived after/within 20 minutes. (Time↝Interval) Interval#005

I reached the summit in 3 days. [= 3 days later, I reached the summit.] Interval#008

I was at the summit within 3 days. [= 3 days later, I was at the summit.] Interval#009

I finished climbing in 3 days. [= 3 days later, I finished climbing.] Interval#010

They had the engine fixed in 3 days. [= 3 days later, they had the engine fixed.] Interval#011

We left the party after an hour. [an hour after it started] (Time↝Interval) Time#014

We left the party an hour ago. [an hour before now] (Time↝Interval) Time#015