"Survive for 2 days straight" was a major challenge. But I found an interesting bug in Alto's Adventure that made it easy. First, crash at the far lip of this particular chasm:

chasm

As far as I know, it does not work on any other chasms. You mustn't fall into the chasm. It's usually enough to land just short of the lip, maybe not quite upright.

Next, sit there for 2 days :)

The sun and moon will go around, it will be peaceful. You'll probably sit through a rainstorm or snowstorm but you a) won't have to do anything except keep your screen awake from time to time, and b) won't have any pesky elders chasing you. By the timestamps on my screenshots, I waited about 6 minutes.

Once you've sat there long enough, just tap the screen and you'll jump to life again and be on your way. You can see I'm around 12,407 meters here and then here:

I'm at 12,568 meters and the sun is just coming up again for the third time this round.