We've been looking into this too and here are our dates (for info we have come from the UK):
Blue PR sticker issued 6th August 2007
Arrived in NZ 11th August 2007
So year one is 11th Aug 2007 to 10th Aug 2008 and so on in 12mth periods.
You need to have been in NZ for at least 1350 days in the five x 12mth periods since landing AND been here in NZ for 240 days in each of those 12mth periods.
These means that we become eligible to apply for citizenship on (IIRC) 9th April 2012 NOT our 5th anniversary of landing here which is 11th Aug 2012 as we previously believed.
I've confirmed all this by phone with DIA.
Some other UK ex-pat friends of ours have just been through the application process and said they just took all the necessary paperwork to the DIA in Auckland (you need to book an appointment) and it took about an hour. They do all the autenticating of photographs and photocopying whilst you wait. It cost them $470.20 per adult. After approx. 6 weeks they got a letter approving them and now they are waiting for the ceremony so that they can apply for passports.
Please note this is all as at March 2012 and is what we have found out about our particular situation.
HTH
Mrs B.