What is the difference between 갱신 (更新) and 경신 (更新)?

ANSWER: 갱신 (更新) means "to renew," which suggests "extension," and 경신 (更新) means "to revise," which suggests "change." So, 갱신하다 is used when talking about "renewing" one's passport or driver's license, and 경신하다 is used when talking about breaking world records in sports or production records in manufacturing, which means those records are changed or "revised."

One of the interesting things about the two Sino-Korean words 갱신 (更新) and 경신 (更新) is that they both use the same Chinese characters. When the Chinese character 更 is pronounced as /갱/, it means "anew" or "again," but when it is pronounced as /경/, it means "to change" or "to alter." So, since the Chinese character 新 (신) means "new," the word 갱신 (更新) literally means "renew," and 경신 (更新) literally means "to change to (更) a new one (新)."

In the following definition of the Chinese character 更 (갱/경), notice that 갱신 (更新) is mentioned but not 경신 (更新). Also, notice that 갱신 is defined as "renewal" or "renovation," which could be suggesting that 갱신 can be used to mean both "to renew" (a driver's license) and "to revise" (a world record). In fact, when I looked up 경신 in my 2014 edition Minjung's Essence Korean-English Dictionary, it was defined as "renewal" and then listed a reference to the word 갱신, which seemed to suggest that 경신 and 갱신 mean the same thing. In other words, my Essence dictionary is saying that 갱신 can be used both when talking about when renewing driver's licenses and breaking world sport's records.

By the way, I wonder if the word 갱신 (갱신) originally came about after people from certain regions of Korea started mispronouncing 경신 (更新). /갱/, for some reason, sounds like it might be a dialectical pronunciation.

A Guide to Chinese Characters: Reading and Writing Hangul and Hanja (1982)

Minjung' Essence Korean-English Dictionary (2014)

In addition, my 1998 edition Dong-a's Prime Korean-English Dictionary seems to have gotten the meanings of 갱신 and 경신 mixed up, saying that 갱신 is used when talking about breaking world sport's records, and 경신 is used when talking about renewing driver's licenses, which is backwards from the way they are supposed to be used.

Dong-a's Prime Korean-English Dictionary (1998)

So, whom should one believe in regard to the meanings or 갱신 and 경신? Well, I believe the "Modern Girl," the girl who made the video below, and the Modern Girl's simple "hack" (꿀팁) for remembering the difference between 갱신 and 경신 is this:

계약을 갱신하다 (renew a contract).

기록을 경신하다 (break a record).

In regard to "contracts," however, the Modern Girl does point out that sometimes they are "renewed" (갱신) and sometimes they are "revised" (경신), which means that sometimes we might say, "계약을 갱신하다" (renew a contract), and sometimes we might say, "계약을 경신하다" (revise a contract).