The idiom "a day late and a dollar short" generally means that someone has both missed an opportunity and been inexcusably unprepared for it. A briefer translation of this saying could be "too late and too little." It can also refer to an unfavorable review of a person's efforts as poorly timed and too inadequate to make any improvements to a given outcome. This phrase is often characterized as one of the English sayings that place underlying importance on time and money. Preparation and organization are usually highly valued in cultures that use these kinds of idiomatic expressions.
Sayings such as this frequently express somewhat negative feelings towards another person, namely disappointment and even frustration. Meanings of idioms are usually unique to a certain language, and English is no exception. The words and phrasing of "a day late and a dollar short" may often seem confusing at first to a non-native speaker. Linguistic definitions of idioms generally characterize them as having words whose direct meanings are not immediately obvious. Even though many second language English learners may at first find this kind of idiom difficult to understand, many of them still want to learn its correct use in order to speak the language more naturally.
Idiomatic expressions are also sometimes spoken euphemistically when the speaker prefers to stay polite or sometimes politically correct. Telling someone that he or she is "a day late and a dollar short" is often perceived as kinder than directly saying that he or she is habitually late, disorganized, careless with time management, and even inconsiderate of others. Since a day is a relatively short amount of time and a dollar is a relatively small amount of money, this idiom generally implies that someone is rather close but still not quite good enough to measure up. The phrase can also sometimes be interpreted as a subtle admonition to adequately prepare for and fulfill given responsibilities and others' expectations.
The phrase has its origins in the United States, although it is somewhat unclear exactly when this idiomatic expression first became part of the common American English language. Some researchers suggest that it dates back at least a century. The phrase has also appeared in several pop culture references, including book and song titles that date back several decades.