You can find the date range of the report you're viewing at the beginning of the sentence above the chart.
if you click on the date range, you will see a Date Range dialog box that will allow you to select different date options.
To use a custom date range, click into the boxes at the bottom of the date-picker dialog and type in your own dates:
If you use a fiscal year that starts on a date other than January 1st, contact support to have this configured for you.
Once you have a fiscal year configured, you will see a column in the Date Range dialog box with fiscal date options on most reports.