Group Views results by split year (academic, fiscal, etc.)
Use Grouped Exposed Filter

Using a Grouped Exposed Filter for the Authored on field is the quickest and easiest way to filter out by academic year. 

When you Expose a Filter, you can choose between Single filter and Grouped filters: 



If you choose Grouped filters you can define your own items for the Exposed filter. In your case two academic years would be configured like this: 



I haven't included time but you probably should to make sure that content created on July 31 and August 1 doesn't get exluded. Maybe something like 2017-08-01 00:00:00 and 2018-07-31 23:59:59 would work. 

Add as many entries as you have academic years. Then when viewing your Views results choose the appropriate academic year option: 



I've noticed grouped filters have some bugs in D8 when dealing with taxonomy terms, but I haven't noticed any problems with AuthoredOn field. 



Contextual Filter Content: Created year + month

If you include this Contextual Filter and choose to Display a summary: 



you get links of months and years you click through to see content posted within those dates: 



If that alone isn't enough maybe that can inspire you to create a similar custom Contextual filter with a bit more logic inside to do the same but for a configurable set of periods.