When cast to text, the output depends on the
jira.date.time.picker.java.format parameter set in your Jira instance.
19/Mar/20 1:38 PM would be returned for
dd/MMM/yy h:mm a
If you want to return a number (a timestamp) instead, remove the leading % character in front of the field code.
You will not be able to do this in the basic mode. Learn more about Parsing modes.