不惑之年 Age without confusion
Explanation
指四十岁。四十岁的人，一般来说，已经经历了许多事情，对人生有了比较清醒的认识，不会再为一些小事而迷惑。
Refers to the age of forty. At the age of forty, people have generally experienced many things and have a clearer understanding of life, and they will no longer be confused by trivial matters.
Origin Story
春秋时期，孔子周游列国，历经磨难。一次，孔子与弟子们在蔡国避难，生活困窘。面对困境，孔子却显得平静而睿智。他告诉弟子们，他三十而立，四十不惑，五十知天命，六十耳顺，七十从心所欲不逾矩。四十不惑，并非指没有疑惑，而是指能够明辨是非，不为外物所惑，能够从容面对人生的挑战。孔子以自身经历告诫弟子们要坚守信念，即使身处逆境也要保持内心的平静与坚定。弟子们深受启发，更加坚定了跟随孔子的决心。
During the Spring and Autumn Period, Confucius traveled through various states, experiencing many hardships. Once, Confucius and his disciples took refuge in Cai, where they lived in poverty. However, Confucius remained calm and wise. He told his disciples that he was steadfast at thirty, without doubt at forty, understood destiny at fifty, obedient at sixty, and did what he wanted without exceeding the rules at seventy. "Without doubt" does not mean that there are no doubts, but that one can distinguish right from wrong, is not confused by external things, and can calmly face life's challenges. Confucius admonished his disciples with his own experiences to uphold their beliefs and maintain inner peace and firmness even in adversity. The disciples were deeply inspired and strengthened their resolve to follow Confucius.
Usage
常用来指四十岁，或用来形容人到四十岁时对事理的通达。
Often used to refer to the age of forty, or to describe a person's understanding of things and principles at the age of forty.
Examples
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他不惑之年便已功成名就。
ta bu huozhinián bian yi gongchengmingjiu
He had already achieved great success in his forties.
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他到了不惑之年，对人生有了更深的理解。
ta daole bu huozhinián dui rensheng youle geng shen de lijie
In his forties, he had gained a deeper understanding of life