I’ve made an app that makes it possible to schedule a post in Lemmy at an arbitrary time. It’s available at https://schedule.lemmings.world and can be used by people from any instance.
Let me know what you think!
P.S. This post is made using the app!
Edit: And it’s open source!
I used it for example to post this very post at a time when people from US are most likely to engage (though I’m not sure if the Lemmy demographics is predominantly US, but my gut feeling is it is).