I tried using the Rule Engine node and it worked for me. Note the quotation marks in the rule.
There is no documentation in the node description on the accepted format. I also noted some strangeness in that the Rule list disappeared when I opened the dialog a second time (then reappeared when I opened a third time - using KNIME 3.6.0 on windows).
A (better IMHO) alternative is to use the Date and Time Difference node to calculate the difference between the LastPurchaseDate values and 2011-11-09 (see config screenshot below), followed by a Rule Engine node to convert negative values to “Y”.
Thanks Don, I tried the Rule Manager with the string you showed in the screenshot and this worked well and solved my issue. Just a quick follow-up question - how do I add an ‘else’ in the statement so that all the rows which does not meet the criteria has the flag 'N" instead of blank or red '?"?