Date Calculation

Hi, community

I've created this DAX, For the getting dates for previous months. 

But when I'm doing m1-1, I'm not getting proper values. 

If I've selected Nov month then I should be getting 31st Oct 2021. But it's showing 30th Oct. Considering 30 days for each month.

Any solution for this.? Because I want the Previous month's last date that's why I did m1-1. 

And "selected-max-dates = MAX(Dates)"