I'll keep this brief since I know technical info can be a little dry :lol:
In Ecclesiastes, time is mutable. That means you can go back in time, change something, and drastically alter the future. These alterations occur through temporal distortion waves that propagate forward in time, starting at the point of the change and moving towards the future. The only way to avoid being "rewritten" by the distortion wave is to either "hop" over it (jump before it so it doesn't ever hit you) or to take shelter in a temporal exclusion safe zone like Ecclesiastes station. Once the wave has passed, anyone can leave the exclusion zone without fear of being rewritten
In this way, the crew of Ecclesiastes station can address changes to the timeline even if a distortion wave has overwritten the present.
Please let me know if you have any questions about this. ;)
A nice example of time travel which works more or less the same way is Voyager "Year of Hell" Parts 1 and 2 (http://en.memory-alpha.org/wiki/Year_of_Hell_(episode)).
A major inspiration for this SRP!