My thinking:
If we bought it today, tomorrow is start of year 1, day 1. (could be day two, but lets ignore that part)
26 Aug 2017 is start of year 2 day 1.
26 Aug 2018 is start of year 3 day 1.
26 Aug 2019 is start of year 4 day 1.
26 Aug 2020 is start of year 5 day 1.
26 Aug 2021 is start of year 6 day 1.

hope that helps. I dont know if im right tho. As I know there is no year zero, so it has to start at year one which includes part thereof.