1572,the year of FF8.

[Future Esthar]

They travel to the future.
The Propagators will be destroyed by Squall as we know.
A better question is how can Squall and Rinoa battle themselves?
Time is not set on stone on FF8.
The lost Ragnarok was controlled through junction waves by Hyne.
Hyne somehow used the Ragnarok to capture each pair on each era(kinda like Noah´s ark).Don´t forget the Ragnarok can time-travel.
But there were different "Universes" on FF8 where the outcomes of destiny differ.
And they were brought from the past to the future.
Hope that clarifies your questions,Crazybayman.