I am trying to run a report to encompass multiple days, but it's not capturing the final day of information, why? 

There are two workarounds you can use. 

1. You will want to adjust the time on the End Date to be 11:59 PM instead of the default 12:00AM.

2. You will want to select the next day and keep the 12:00AM end time. Ex: You want the report to run from 01/01 to 01/06. You will set the Start Date field to be: 01/01/2021 12:00AM. The End Date field will be 01/07/2021 12:00AM to encompass all of the information contained for the day before.