Knowledge cutoff
The knowledge cutoff is the date after which a model has no information from its training data. Unless the tool searches the web or your documents, it won't know about events, prices or laws that changed later.
In one line, for a 12-year-old
The knowledge cutoff is the day the AI stopped reading the news.
An example
Ask about this year's tax-filing deadline and a model without web search may give you last year's date.
Why it matters to people
Out-of-date answers about benefits, health or the law can cause real harm. Check anything time-sensitive against an official, current source.