If I interpret the first link properly, X is the predicted finish date and Y
is the date at which the prediction was made. For each line on the chart,
you need a column of predicted dates and prediction dates. Make an XY chart
from the first pair of date columns, Double click the vertical axis, and
change the scale so it plots in reverse order and the axis crosses at the
maximum. Copy each successive pair of data columns, select the chart, and
paste special as a new series with the X (category) data in the first
column.