Dashboards are not the same as reports. When you open a report, the report data will be generated based on current data. On the other hand, for dashboards, when you open a dashboard, it will show the data as of the latest dashboard refreshed by any users or by a schedule.
All users able to view the dashboard will be able to refresh the dashboard by simply clicking on the Refresh button after opening the dashboard. Even users who do not have permission to edit the dashboard are able to refresh the dashboard. Once refreshed, the other user that sees the dashboard will be based on latest refreshed data.
Notice that in the following screenshot, information under the dashboard title will show us the data used for the dashboard, which is the same with the latest dashboard refresh:
But if the dashboard hasn't been refreshed in 24 hours, it lets you know with...