In 1946, some 364 of the 1,850 general use Chinese characters, or Tōyō Kanji (当用漢字), were simplified. Today, Japanese 1st graders learn 学 instead of 學; 気 rather than 氣, 糸 not 絲, and so on. In Taiwan and Hong Kong, the older characters (旧字体, kyūjitai) are still in use.
The list of Tōyō Kanji was replaced by a list of 1,945 Jōyō Kanji (常用漢字) in 1981. Further revision of the list occurred in 2010, including an additional 196 characters, and the removal of 5.
Incidentally, this is news to me. I have been operating under the assumption that the number of Jōyō Kanji has always been 1,945. What message was the Ministry of Education trying to convey by that conspicuous number, I always wondered.