[Help] Creating a bar chart with one sided rounded rectangle

[dennismphil]

Happy New Year!

I need a bit of help in creating the chart shown below. 

The columns need to be rounded on the top end only and the y-axis dates need to be formatted so that the y-axis formatted date labels are aligned with the center of the bars. 

How would you go about implementing this?

Notebook

https://observablehq.com/d/5488d85cbe5f8d48