If I understand you correctly you want two string properties containing the formatted string version of the current date and time?
I was able to get the forrmatting to work by adding two string properties to one of my transactions with each property being set to an initial value of Rule - before data entry.
Attached are screen shots of my two properties and the associated rules. I tried inserting but am having trouble so hopefully they will attach as expected. When the transaction started the properties are set to the corresponding values as expected.
Hope this helps!
--Bill