You don't need to use Calendarauto. In the PowerPivot window, click the Design ribbon and then Date Table > New. That will create a date table from the first year to the last year of the data in your model.
Thanks Ingeborg, I am preparing for 70-779 Analyzing and Visualizing Data with Excel, and CALENDAR AND CALENDARAUTO are part of the Excel Power Pivot Help. I was just trying to confirm, if this is possible and I have been using the Design ribbon Date Table > New command. I will now assume you can only use this in Power BI and maybe other applications that use DAX (e.g. SQL). Thanks.
AFAIK, PowerPivot for Excel does not allow creating a new table the way that Power BI does. The CalendarAuto formula is still available in DAX for PowerPivot, because it returns a table of values. That resulting table can be used nested in other DAX formulas to create calculations and measures.