Plotting multiple date values on a reference axis

I work with datasets that have multiple date/time values per row for task and activity type tracking.

I'm trying to vizualize the data against a reference axis rather than having to chose just one of the columns to be the x-axis.

For example, assume I have 10 tasks.  Each has a start date and some of them have an end date:

I want to know, for any particular time period, how many tasks have started and how many have finished eg I could summarize by month and calculate a 'to date' value:

And I can chart this type of data easily enough in Excel by building a reference date range to plot against:

If I create measures in Power BI and try to plot them I have to select either the Start dates or End dates as the x-axis which results in one of my measures being plotted incorrectly:

Here, the first task with an End date (#1 ending on 1/5) isn't plotted at 1/5/2017 on the x-axis but at 1/8/2017 which is when the next 'Start' date falls.  Similarly the 2/10/2017 End for #2 doesn't appear at all, and the 2/12/2017 End for #3 appears at 2/21/2017 as total to date = 3.

I don't know if I can fix this by just changing my measures, but I figure I need to create some other refernce timeline to act as the x-axis.

Measures used:

YTDStart = CALCULATE ( COUNTX ( Tasks , [Start] ) , FILTER ( ALLSELECTED ( Tasks ) , [Start] <= MAX( [Start] ) ) )

YTDEnd = CALCULATE ( COUNTX ( Tasks , [End] ) , FILTER ( ALLSELECTED ( Tasks ) , [End] <= MAX ( [Start] ) ) )