Here's a breakdown of the historical context:
* Early Stages: Mandarin dialects, particularly the Beijing dialect, were already gaining prominence during the Ming and Qing dynasties. They were used in government and literature, but not formally declared as a national language.
* Post-Revolution: After the 1911 revolution, a national language movement aimed to unify China through a standard language. The Putonghua (Common Language) based on the Beijing dialect emerged as the chosen standard.
* Official Recognition: In 1955, the People's Republic of China officially adopted Putonghua as the standard national language. It's important to note that Putonghua is not the same as Mandarin; it's a specific dialect that was standardized as the official language.
* Present Day: Today, Mandarin Chinese (which includes Putonghua) is the official language of Mainland China, Taiwan, and Singapore.
Therefore, while there isn't a specific "official declaration" date, the process of establishing Mandarin as the national language was gradual and evolved over time.