If you setup your date filter as 'Special' filter and choose 'All dates' then, every time your data refreshes, the slider will point to the most recent date in your dashboard (i.e. include all values).
Give it a try and let me know if this helps. Share your workbook if you still have issues with it.
Thanks, Devarsh. What do you mean by "Special" filter?
And to clarify, I'm not refering to the slider on a date filter, I am referring to the horizontal slider for the dashboard pane.