No specific timeline
Thor was an idiot. He fumed as he pulled the cloak closer around him to disguise the distinctly Jotun blue tint that had been forming in this blasted weather.
It was one of those rare occasions where Loki was let out of prison to fix Thor's messes. If that didn't show that Thor was a complete imbecile, he didn't know what would.
This time, Thor had made a rash bet to a Frost Giant, putting something that was no doubt precious on the line. Loki hadn't been told what it was. To prevent him from stealing it himself, most likely.
The only reason he actually needed to be here, on a planet he had tried to annihilate not five years ago, was because his brother had agreed to a horse race. It made sense, therefore, to use the fastest horse at their disposal.
Unfortunately, that horse had outright refused to help, turning in a huff and kicking at Thor when he attempted to saddle it. Even Odin couldn't get the stallion to listen.
So that was why the golden haired prince had let him out of his (actually rather comfortable, but most importantly warm) cell. To play babysitter to a stubborn equine who would only listen to him.
Thor was an idiot
"Your steed may have an impressive number of legs, Asgardian, but ours is a purebred Jotun steed! Fathered by the legendary stallion Falhofnir and birthed by the great mare Gisl!" The Frost Giant bragged.
"Well," Thor began angrily, and Loki could feel the alarm bells going off in his head as his brother grabbed him by the shoulder and patted the horse with his free hand.
"Our steed is half-Jotun!"
Thor was an utter idiot, Loki reflected as he kicked his brother's shin and glared at a snickering Sleipnir.
RnR!