Associate
Or perhaps 'how will you know?' is better phrasing.
Like I said, when it's following something approaching normal patterns for a couple of weeks. It's not an exact science (as much as some people will pretend otherwise) and if you're investing for the medium / long term then it doesn't have to be. You just don't want to see a severe loss in the first couple of weeks due to a once in a generation (possibly) crash.
People who are trying to beat the benchmarks will have their own strategies, but as they're always based on historical data I think their utility is probably limited in situations like this. Even professional investment houses with effectively unlimited resources and preferential deals struggle to consistently beat benchmarks.