At what point does the "past" become part of "history"? Is there a specific time frame?

The joke in grad school was that the past becomes history when a PhD committee is willing to read a dissertation about it.

Hahaha

But seriously, there is no iron-clad answer to this question. Historians study and argue about change over time. If something is recent, there will likely not be a lot of solid information about it. This makes any argument bereft of enough material to be cogent. You can't argue about what you don't know, right? Well, you can, but it'll be terrible.

It's common in lecture to get a question on how something recent relates to the lecture material. My answer is usually something along the lines of 'there hasn't been much scholarship on that yet.' All that really means is that not enough time has passed for source materials and interest to converge in a library somewhere, and the real answer is 'I have no idea.'

So what might be a good answer? Don't know for sure, but I suspect that the time frame suggested is shrinking. 25 years ago, it took a long time for articles and books to filter their way into the Reader's Guide and then into a library catalog, and then into a researcher's hands. Today, that process is much quicker. The sort-of-constant though is that researching and writing a dissertation or book is a long process, so I suspect that in academic terms, we'll never see a point when the past becomes 'history' in less than a decade or so. I could well be wrong.