Q:

How can you make a TFS style rule for blank dates

In a TFS web interface, is it possible to create a kanban board style rule for when a date field is blank? For example, I want to highlight all items in a given column that do no have a date set in one of the fields.
I have the following rule, which I would expect to highlight a card without a set "Design Target" date while in the "In Design" column, but the rule isn't applying to any of the cards. Is there special syntax for blank date?

A:

is it possible to create a kanban board style rule for when a date field is blank?

I am afraid we could not to create kanban board style rule with date field is blank. 
As we know, the type of the date field is Date time:

The value of this date field should be like: @Today or specify dates(Enter dates in the Date Pattern you set for your personal profile).
You can check the document Query by date or current iteration for some more details.
If we set the value is blank, this value is string style not the date type, this should be invalid date value. That is the reason why the rule isn't applying to any of the cards.
If you want to highlight a card without a set "Design Target" date while in the "In Design" column, you can give a large range of values to the Design target, for example:
Design Target > 9/4/2015

Or 
Design Target < 9/4/2022

Hope this helps.

