When I've gotten into discussions in the past to try and point this out, they will pivot and say that "it happened incrementally" and not all at once. This is to try and get around the discrepancies of multiple decades of contradictions. So having some earlier dates and much later dates in your timeline helps because they can only think in terms of the biggest, most celebrated cultural touchstones. Before and after these moments it's all in flux for them so you need to pin the timeline down in a few points so they can picture it all at once.