Pokémon Diamond Version, Pearl Version, and Platinum Version - Trainer ID
The Trainer ID is 32 bits long. The player as well as each Pokémon can have a 32-bit Trainer ID. A Pokémon’s 32-bit Trainer ID is set to the player’s as the Pokémon is created, if it’s owned by that player. A player’s 32-bit Trainer ID is set when a new game is started. However, the game only displays the lower 16 bits of a Trainer ID (here called called "public ID").
Many other Web sites use the term "ID number" or "Trainer ID" to mean the portion of the number visible on the Trainer Card, even though the Trainer ID, as used on this site, is 32 bits long. The "ID number" term used by those sites is 16 bits long and takes the lower 16 bits of the 32-bit ID number. These sites also use another term, "secret ID", which is the portion not shown of the ID and consists of the high 16 bits of the 32-bit ID number.
Each Pokémon also comes with an Original Trainer name ("OT name") and OT gender. (The OT gender is used primarily to color the OT name’s text blue (male) or red (female).) These two values, like the Trainer ID, are set to those of the player as a Pokémon owned by that player is created.
The way each game checks "ownership" of a Pokémon, however, can vary depending on the game and on the specific case, as detailed below.
To rename a Pokémon using the Name Rater in Eterna City, Goldenrod City, or Lavender Town, a Pokémon’s public ID must match that of the player.
If a Pokémon’s 32-bit Trainer ID, OT name, or both (but not necessarily OT gender) are different from those of the player, it can disobey unless the player has the appropriate badges, and it will gain extra Exp. Points (see below).
The game says that a Pokémon was "apparently" met, "apparently" hatched from an Egg, or "apparently" had a fateful encounter (as the case may be) if its 32-bit Trainer ID, OT name, OT gender, any two, or all three are different from those of the player. This doesn’t apply if the Pokémon "arrived" from a different region not in the game.