Different historical periods will produce different revolutionary spirits. When did Yan 'an Spirit come into being?

Yan 'an Spirit: 1942 12 In February, Mao Zedong put forward Yan 'an Spirit for the first time at the meeting of senior cadres in the Shaanxi-Gansu-Ningxia Border Region.

Yan 'an spirit was formed by China in Yan 'an rectification movement and mass production movement. Yan 'an spirit is: the spirit of hard struggle; The spirit of serving the people wholeheartedly; The spirit of integrating theory with practice and constantly pioneering and innovating; The spirit of seeking truth from facts.