This depends on if you are learning a new programming language, or a new paradigm. Many languages share paradigms (the core concepts of OOP are the same in all

This depends on if you are learning a new programming language, or a new paradigm. Many languages share paradigms (the core concepts of OOP are the same in all major high level languages, for example) and only differ in syntax. It's easy to bounce between those languages. But some languages require totally new ways of thinking, and you're not going to learn that in a day if you haven't been exposed to it before. In fact, I would even say this line of thinking -- "I can learn it in a day" -- can be dangerous by causing you to ignore the idiosyncrasies of the new language, causing bugs you don't understand the root cause of. This is a problem you commonly see when experienced programmers start coding Javascript without reading about prototypes, closures, etc.