4 month sleep regression

Might be a dumb question but I have to ask:

For those of you posting about currently or already have gone through the 4 mo sleep regression (I assume with current babe), how do you know you’re actually in it if only few August babies are just now turning 4 months?

I know there’s a range of time it hits, but I fear that if I call what we are currently in the regression, I may be wrong and it will really happen in a few weeks lol.