一日之长 a day's advantage
Explanation
这个成语的意思是：长：长处。表示判断或处理事情有稍强于他人的能力。例如，在处理某项工作时，虽然你比别人年轻，经验少，但你对问题的理解和解决方法却更胜一筹，就可以说你在这方面“一日之长”。
The meaning of this idiom is: 长 (cháng): advantage. It means that one has slightly more ability than others to judge or deal with things. For example, when dealing with a certain job, even though you are younger and less experienced than others, but you have a better understanding of the problem and solutions, you can say that you have "一日之长" in this aspect.
Origin Story
传说战国时期，齐国的大臣淳于髡，才华横溢，口才出众，常被齐王派去做外交使节，受到许多诸侯国的礼遇。有一次，齐王问他：“你认为你和晏婴相比，谁更出色？”淳于髡毫不犹豫地回答：“我比晏婴稍胜一筹，论王霸之余策，览倚仗之要害，我似有一日之长。”齐王听了很高兴，就问他：“那你说说，你比晏婴强在哪里？”淳于髡说：“晏婴曾经说，如果要治国，就要先了解国情，然后才能制定政策。而我则认为，不仅要了解国情，还要了解人心。只有了解了人心，才能制定出更加有效的政策，才能真正得到百姓的支持。”齐王听后深以为然，从此更加器重淳于髡。
It is said that during the Warring States Period, Chunyu Kun, a minister of the State of Qi, was a brilliant man with exceptional eloquence. He was often sent by the King of Qi as a diplomatic envoy and received much courtesy from many feudal states. Once, the King of Qi asked him: "Do you think you or Yan Ying is better?" Chunyu Kun answered without hesitation: "I am slightly better than Yan Ying. In terms of the remnants of the royal and hegemonic policies, and the important points of support, I seem to have "一日之长".
Usage
这个成语通常用来形容某人在某个方面比别人略胜一筹，但也只是比别人稍强一点，并不表示完全超过。
This idiom is usually used to describe someone who is slightly better than others in a certain aspect, but only slightly better. It doesn't mean they completely surpass others.
Examples
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虽然他年轻，但处理问题却比老练的人更有见地，真是“一日之长”啊。
suīrán tā nián qīng, dàn chǔ lǐ wèn tí què bǐ lǎo liàn de rén gèng yǒu jiàn dì, zhēn shì 'yī rì zhī cháng' a.
Although he is young, he has more insight into solving problems than experienced people, a true "一日之长"!
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在这次竞赛中，他虽然没有获得第一名，但在某些方面确实“一日之长”。
zài zhè cì jìng sài zhōng, tā suīrán méi yǒu huò dé dì yī míng, dàn zài mǒu xiē fāng miàn què shí 'yī rì zhī cháng'.
He didn't win first place in this competition, but he is indeed "一日之长" in some aspects.