Custom Year column between dates

Hi, 

I need to create a custom Year column based on between dates

Between

01/09/2014 and 31/08/2015 then 14/15 else

01/09/2015 and 31/08/2016 then 15/16 else

01/09/2016 and 31/08/2017 then 16/17 else

01/09/2017 and 31/08/2018 then 17/18 else

01/09/2018 and 31/08/2019 then 18/19 else

01/09/2019 and 31/08/2020 then 19/20 else

01/09/2020 and 31/08/2021 then 20/21 else

01/09/2021 and 31/08/2022 then 21/22 else

01/09/2022 and 31/08/2023 then 22/23 else

any idea what the correct syntax to use on this would be, please?