Start/End Dates	2013-08-10 through 2013-09-06
Country	Japan

Details

Satoshi's Pikachu, Iris' Kibago, Dent's Yanappu and Okido's Rotom were all distributed to the Japanese players of Black, White, Black 2 and White 2 from August 10th, 2013 until September 6th, 2013. The Pokémon will be distributed at the Pokémon Centers in Japan and there was four separate distribution periods.

Distribution Periods

Period 1: August 10th, 2013 to August 16th, 2013
Period 2: August 17th, 2013 to August 23rd, 2013
Period 3: August 24th, 2013 to August 30th, 2013
Period 4: August 31st, 2013 to September 6th, 2013

Source: http://www.pokemon.co.jp/info/2013/07/130726_g01.html