You can maybe find a warrior or warlord along the path that has a coded Pokemon like Gible, Dratini and Pikachu, but usually their Link % is low and below 50, which gives very little chance of evolving and powering up the Pokemon. Using the code allows for many warlords to get the pokemon with a high link % (above 70). I've yet to seen a wild coded pokemon.
And, it's all game time. So 1 month = 1 month in the game, not outside.