When in Reports you can choose what dates are displayed by clicking on the Calendar View
First, you will want to click on the Calendar View.
You will then want to go to the beginning date and make sure only this date is highlighted.
From there you will click through the, < >, until you come to the month you would like your report to end.
You will then select the end date, making sure it is highlighted and your dates are showing correctly above.
You will then be able to generate a report for the dates you selected..