After King Wu of Zhou, Ji Fa, conquered the Shang dynasty and established the Western Zhou, he died before completing his grand mission. His son, Ji Song, inherited the throne as King Cheng of Zhou, but at just thirteen years old, he relied on his uncle, the Duke of Zhou, Ji Dan, to govern the realm.
Ji Dan, the Duke of Zhou, was a brilliant statesman in the early Western Zhou Dynasty. He played a key role in his brother Ji Fa's campaign to conquer the Shang Dynasty. After taking on the heavy responsibility of assisting in state affairs, he devoted himself wholeheartedly to strengthening the Zhou regime. Whether he was eating or attending to personal matters, whenever official business arose, he would immediately set aside everything to handle it.
In the early days of the newly founded Zhou Dynasty, the political situation was far from stable. Some nobles, suspicious of the Duke of Zhou, spread rumors before King Cheng, accusing him of harboring ambitions to usurp the throne. Meanwhile, the king's own brothers conspired with Wu Geng, the son of the deposed Shang king, launching an armed rebellion. Taking advantage of the chaos, the Yi tribes in the east also rose up. But the Duke of Zhou, unwavering and resilient, followed the will of King Wu. He cleared King Cheng's misunderstandings, crushed the rebellion of Wu Geng and his allies, subdued the Yi tribes, established a code of rites and laws, continued enfeoffing feudal lords, and built the city of Luoyang (in present-day Henan), establishing the eastern capital Chengzhou.
Shortly after establishing the Eastern Capital, the Duke of Zhou died from overwork serving the state. On his deathbed, he earnestly advised his ministers to assist the Son of Heaven in governing the Central Plains, and instructed that he be buried in Chengzhou as a symbol of his unwavering loyalty to the king's command even in death.
Mencius of the Warring States period held the Duke of Zhou as the ideal ruler, praising his tireless dedication to state affairs. Mencius remarked, "The Duke of Zhou sought to combine the virtues of the founding kings of the Xia, Shang, and Zhou dynasties to govern well. If something didn't suit the times, he would tilt his head and think. If he couldn't solve it by day, he continued at night. Once he found a good solution, he would sit waiting for dawn, then immediately put it into action."
Later, the idiom "night and day" came to describe working continuously without stopping, regardless of day or night.
Source: *Mencius*, Chapter "Li Lou"
Meaning of the Idiom: Later, the Chinese idiom "夜以继日" came to describe working continuously without stopping, regardless of day or night.