If your renewal is say the 01/09/06 then the number of years no claims you have is up until the renewal date, even though your renewal certificate / schedule will say from 01/09/06 until 01/09/07 which is the new policy year.
The reason they do this is insurance companys will only give you what you have earned and not what you could also they do not know what the new insurance year will hold for you claims / convictions etc....
Hope that helps a little.
Alan.