Please provide a way to define a date.
For example:
@startuml !define THE_DATE %date% Title Generated THE_DATE @enduml
(--------)
With last beta https://dl.dropboxusercontent.com/u/13064071/plantuml.jar
You can have:
@startuml !define THE_DATE %date% !define ANOTHER_DATE %date[yyyy.MM.dd G 'at' HH:mm:ss z]% Title Generated THE_DATE or ANOTHER_DATE alice -> bob @enduml
The format for date is defined here: https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html