In the late Tang Dynasty, the chaos of warlord conflicts far surpassed the similar turmoil at the end of the Eastern Han Dynasty. While the Eastern Han's wars resulted only in the Three Kingdoms, the late Tang's conflicts gave rise to the Five Dynasties and Ten Kingdoms.
Among the powerful warlords of the late Tang Dynasty was Li Keyong, son of the Shatuo chieftain Zhuye Chixin. After Zhuye helped Emperor Yizong crush a rebellion, he was granted the imperial surname Li, renamed Li Guochang, and appointed military governor of the Datong Army. Li Keyong himself, for suppressing the Huang Chao Rebellion, became military governor of Hedong, and later, for pacifying Youzhou, Emperor Zhaozong enfeoffed him as the Prince of Jin. This nominal Tang subject, seeking to control the imperial court, waged a brutal series of battles against his rival warlord Zhu Wen.
Li Keyong's chief rival, Zhu Wen, was originally a general under the rebel leader Huang Chao. When the rebellion faltered, Zhu Wen betrayed Huang Chao, surrendered to the Tang court, was granted the name Zhu Quanzhong, and appointed military governor of Tonghua. Ruthless and cunning, he turned on his former comrades, slaughtering the rebels. As Huang Chao's forces crumbled, more defectors flocked to Zhu Quanzhong, building his power on a foundation of traitors. Soon, he seized Emperor Zhaozong of Tang, was enfeoffed as Prince of Liang, and took full control of the imperial government. In 907, he forced the emperor to abdicate, and Zhu Quanzhong finally ascended the throne as Emperor of the Later Liang.
Despite this, Li Keyong still clung to the fantasy of replacing the Tang emperor. At the time, the warlord Wang Jian, who controlled Sichuan and would later found the Former Shu Kingdom, sent a letter urging Li Keyong to remain the Prince of Jin, wait for the right moment to defeat Zhu Quanzhong, then seek out a Tang imperial heir to restore the throne, and finally retreat to his own territory as a vassal. These ambitious warlords had not yet discarded their pretense of loyalty to the Tang. Li Keyong refused to listen. He wrote back to Wang Jian, rejecting the advice, saying, "There is no fixed order between ruler and subject; hills and valleys shift. Sometimes a long river is blocked, or a deep valley is sealed with mud. Times change and affairs transform—the principles are infinitely varied."
The implication was clear: who should be emperor and who should be a subject was far from settled—time passes, the world changes, and the principles governing it are endlessly shifting. This fully exposed Li Keyong's unwillingness to bow as a vassal and his burning ambition to claim the throne for himself.
However, within less than a year, Li Keyong breathed his last, ultimately failing to realize his ambitions.
The idiom "shifts in time, changes in events" means that as time passes, worldly affairs also change. It is also written as "shifts in time, changes in matters."
Source: *Old History of the Five Dynasties*, "Biography of Emperor Wuhuang, Part Two"
Meaning of the Idiom: Later, the Chinese idiom "时移事改" came to describe as time passes, worldly affairs also change.