How to find the Sum of number days in month between two dates

[Euto]

Hello, I would need help in figuring out how to calculate occupancy rate given the following sample data.

- There's 1 City, and 4 Stores.

City	Store	Status	StartDate	EndDate
A	1	Occupied	January 10, 2020	August 15, 2020
A	1	Occupied	August 26, 2020	December 31, 2020
A	2	Occupied	January 1, 2020	May 3, 2020
A	2	Occupied	May 21, 2020	May 22, 2020
A	2	Occupied	May 23, 2020	August 9, 2020
A	2	Occupied	August 20, 2020	December 31, 2020
A	3	Occupied	January 1, 2020	August 25, 2020
A	3	Occupied	August 26, 2020	December 31, 2020
A	4	Occupied	January 1, 2020	May 9, 2020
A	4	Occupied	May 10, 2020	December 31, 2020

See below what the desired result will be, the Occupancy Rate is what I desire to have.

This is only a sample data, in the actual dataset number or cities are over 100, each of those cities could have 4 - 144 stores each, and the period looked on is over 3 year period(2017, 2018, 2019, 2020).

- I would prefer not to go the route of listing the dates between start and end date in power query.

Additional Edit after initial post:
Sorry I made some changes to dates and changed the desired result to show some vacancy in Jan , May and Aug.

Thanks in advance.

[Greg_Deckler]

@Euto - I'm going to mock this up but I am fairly certain this is a variation on the Overlap pattern I just posted to the Quick Measures Gallery recently. https://community.powerbi.com/t5/Quick-Measures-Gallery/Overlap/td-p/1372369