Loaning?

[Football Club]

If I loan a player when do I get him back?

[Toxcatl]

If I loan a player when do I get him back?

Any moment you want.
When you give a player away that doesn't mean he actually leaves your team. Loans work only for association games, and you can use him in all other tournaments (League, Cup, CL / NML) as usual. But even if you suddenly need him for an Asso game, you can take him back any time. Except when a game is in progress or about to begin.