So even on the 17th of September Julie tells Jones that Jeremy rang her at 3:30.....

No when came clean to police she changed the time and noted 3:12 but attributed such to a roomate:
"I have since spoken to Susan and I feel sure that she told me the time that Jeremy phoned was 3:12am."
The part of the interview you are referring to was simply using the times already written in the past not saying she was reaffirming such times. The actual section where she discussed the time had the above quote.
She left out that Susan kept her clock 10 minutes fast which required an adjustment to 10 minutes earlier. So that is why it was changed again subsequently. She subsequently spoke to her other roomates as well one of who said the hour was 2 and she did not recall the minutes though presumably it had to be close to 3 and another who said 3:15. Julie didn't remember the time so she deferred to her roomates that is the clear implication of referencing them over and over again in her various statements and police spoke to them as well of course and confrimed the clock was 10 minutes fast.