forecasting on year&month data

I have a table with a date column (TXdate), and a sales column.

I want to build a chart that plots average sales by month.

The date range is sept 2015 to april 2016.

I also want to forecast sales 3 months in future.

In my table page, I added a hierarchy (mydate) on year,quarter,month of the TXdate column.

On a bar chart, i have y-axis of avg(sales), and for my x-axis, i do "select column", and then select the hierarchy mydate.

When I try to add a forecast (via lines and curves in chart property), it does not forecast, and gives info message "to calculate a curve, the x-axis must use a time hierarchy or be continuous".

But ... my x-axis is the year,quarter,month hierarchy I created.   How can I get the forecast to work?

I am running

side questions: shows 4 sections 1) date , 2) Year through Day of Week, 3) several Year >> selections, 4) several Fiscal selections.   In my environment, I only have the first 2 sections.  Are the "Year >>" and "Fiscal" selections manually created?   How can I create them, so I can try if forecasting works?

- on same jpg, the month show as names like Jan,Feb.  In my chart with mydate hierarchy, month shows as numbers ...  how can I get my chart to show month names instead of numbers?

Thank you for your help.

(1) Answer