When you create a report, you choose a primary and comparison data range in the date selector to view corresponding results in the widgets.
However, you might want to view a particular widget in a different date range. "Data override" feature comes to your help. As the name suggests, it overrides the date range of report with the one you want for that widget.
Click on "Data Override" in a widget, choose the date range and click on apply to see the changes.