If you can pivot the open and close date columns into one on the DataSource tab,
then you could try a running total on a count of the dates as shown in Sheet 3 v10.0 of the attached.
Thanks for your reply!
In your example you have one date in each record and a qualifier of open/closed. In my example I can have 1 or 2 dates for each item.
I can count items by open date, no problem. The issue I have is with the ones with closed dates. Each item might be open and closed within the period of time I want to visualize and I need to count them on both lines.
My apologies, I didn't quite catch.
I think the result of pivoting the open and close dates into one column
is that it gives a common axis to plot both types of dates.
By using a Count of the Dates (instead of a CountD) it should accommodate
for multiple dates for the same item or open and close in the same time period.
I inputted the data you had provided, and got the attached twbx.
In the image attached, I found ItemID 893 present and counted in both
the open and close lines.
Are you doing the pivoting outside Tableau?