My spreadsheet won't sort dates into their proper sequential order.

I've tried doing Format Cells: Date. I still get this same issue. If I put a filter on the dates and sort A to Z I still get this:

11/30/2018
12/1/2018
12/10/2018
12/11/2018
12/4/2018
12/6/2018

Same issue if I sort Z to A. What I WANT is

11/30/2018
12/1/208
12/4/2018
12/6/2018
12/10/2018
12/11/2018

Help, please!