Given the task definition and input, reply with output. Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Passage: Emperor Gegeen Khan, Ayurbarwada's son and successor, ruled for only two years, from 1321 to 1323. He continued his father's policies to reform the government based on the Confucian principles, with the help of his newly appointed grand chancellor Baiju. During his reign, the Da Yuan Tong Zhi (Chinese: 大元通制, 'the comprehensive institutions of the Great Yuan'), a huge collection of codes and regulations of the Yuan dynasty begun by his father, was formally promulgated. Gegeen was assassinated in a coup involving five princes from a rival faction, perhaps steppe elite opposed to Confucian reforms. They placed Yesün Temür (or Taidingdi) on the throne, and, after an unsuccessful attempt to calm the princes, he also succumbed to regicide. Question: When was Geegen the emperor?
1321 to 1323