To add a calendar global filter to a dashboard, select "Add Control" and then choose "Calendar".
Selecting "Calendar" from the "Add Control" pick-list will display a modal for defining the calendar’s interval. To create this filter, enter a unique name and then assign the default start and end dates. These can be fixed dates or Relative Date Variables.
How to restrict query results with this filter: In the chart editor, drag the desired date field into the "Filters" box and select the appropriate modifier (e.g. Between, Later Than, Earlier Than, etc.). In this case, use the Between and Including modifier. Using the two drop-down selectors, pick the Start and End values for the recently created Calendar filter.