(:DATE ?date) (:PRINTLN "Timestamp: " ?date) (:DATE ?date ?time) (:PRINTLN "Event occurred on " ?date " at " ?time)
In the single-argument version, the date and time are concatenated into a single string. The string contains no spaces and is in a format suitable to use as a file name.
In the two-argument version, the date and time are formatted into separate strings, each containing no spaces and each being suitable to use as a file name.