Time turner question

[corinthum]

No: HPFGUIDX 91719

Ryan Weasley asked:

> I was just wondering... I understand how a time turner is supposed to 
> work but, how were Hermione and Harry able to use theirs toward the 
> end of POA to go back and rescue Sirius? (as well as themselves) 
> There was no way that they could have escaped the Dementors to even 
> have a future to travel back from. And yet they did? I'm sorry if 
> this has been explained or if no one understands what I'm even asking 
> but it is really bugging me. Someboby help!

Ah, the logic of time travel.  

The posts "Time Travel- it's narrative function" (79045) and "Time,
Repetition, and the Uber-Dimension" (79045) and the replies to these
cover the topic pretty thoroughly, including the opposing views on the
dimensions and repetitions of time.  

My own thoughts are presented in 79043.  Really short version of my
theory: yes, they did escape the Dementors a first time, but later
altered those events so that the original escape is not a part of the
dimension of time in which the books take place.

- Corinth