From Bulbapedia, the community-driven Pokémon encyclopedia.
The Standard format of the Pokémon Trading Card Game is one of two formats used for officially-sanctioned Play! Pokémon events along with Expanded format. It was previously called the Modified format prior to the 2013-2014 season. It also will be used in the Pokémon Trading Card Game Online.
The Standard format (then referred to as the Modified format) was introduced in 2001. Tournaments in the 2001-2002 season were played in a format that only allowed cards from the Team Rocket set on up through Neo Genesis (with the exception of Sneasel, which was banned). Since then, Play! Pokémon has continued to rotate out sets once per year, usually after the World Championships, to keep the game fresh and, some speculate, to keep players buying cards. The 2009-2010 tournament season did not feature a rotation, and the rotation for the 2010-2011 season rotated out only four sets, keeping roughly two years' worth of cards in the pool. Additional expansions are added to the current Rotation three weeks after they are released in the United States.
If a card in a Standard-legal expansion is a reprint of an older card, all prints of the card can be played in a Standard-legal expansion-legal deck (i.e. Base Set Potion, recently reprinted in Black & White). However, some cards significantly differ in wording between older prints and newer prints (i.e. Charizard from the Base Set compared to its Stormfront iteration); those cards require a reference outside the deck in order to use the older prints in a Standard-legal deck. A reference must be either a new version of the card or a printout of the card's entry from the official Card-Dex.
Foreign language cards
Prior to the 2009-2010 tournament season, foreign-language prints of cards could also be played without limit, as long as the user provided a local-language reference outside the deck. Starting with the 2009-2010 season, however, sanctioned events began to require players to play with cards printed in English or an region's local language (for example, players in the United States are restricted to English cards only, whereas players in Canada can also use cards in French). This caused an outcry in the TCG community, since many American players had invested heavily in Japanese cards, which were generally less expensive, to use in tournaments. As a result, the rules were amended for the 2009-2010 tournament season to allow up to 10% of a player's deck (six cards) to consist of foreign-language cards. Beginning in the 2010-2011 season, Play! Pokémon followed through with their initial plan to allow only English and local-language cards in premier events.
List of Standard formats