It's up to you, really. Consider there was a huge temporal war in the 29th century so you could imagine that the Feds won and make regular trips to neighboring galaxies via Temporal Slipstream Drive or you can say they lost and the "federation" consists of Klingons, Cardassians, Gorn and their subject worlds.
Fanfic is great, it's literally completely up to you.
Thank you, Maxillius.
Do anyone disagree? If so, why?