Why would anyone in Europe, know when the slaves in the US were freed? Or even when the slaves in Brazil were freed? Or Peru? Or Colombia? Or Cuba? I mean won'

Why would anyone in Europe, know when the slaves in the US were freed? Or even when the slaves in Brazil were freed? Or Peru? Or Colombia? Or Cuba? I mean won't every nation have its own history and important days? And it seems to me that those days in every nation will be different. I'd even wager very few of us, (far less than 1%), know what those important days are called in other nations.