My rule at least for email is that having a person or like the sender is more important than the time. People will open emails if they know it's from someone sometimes like the subject doesn't matter I mean always an example next. For B2B brands is like use a personality in your company send it from someone inside your company you don't send it from the company people will open it because it feels like more personal to do that and then days of times it's like sending  for social media what I see that performs better just from what I've tested is early mornings or like later at nights when people are using the platform but I've also seen posts go off on other time