Because the Fediverse uses chronological timelines, and because it has a worldwide audience, it is totally fine to boost your own post later so it can reach people in different time zones.
There's no algorithm deciding what people see in their main Fediverse timeline, so they just see whatever happens to be there when they are online.
@RyunoKi
It is, but you would have to unboost it first.
Just to note, as someone else pointed out in replies, it's good to be mindful of how often the same people see the same message.
The main idea is boosting later in the same day so that different time zones see it, rather than showing it multiple times to the same people.