The KnowledgeofTime plugin recently linked and discussed, does NOT appear to work with our current version of HAL without causing some operational issues during a conversation. Usually an error box will pop-up stating that there is a Syntax error in a particular line and position saved in halscript.dbg. When checked, it appears the same as other lines of code bearing the exact wording.
Again, not sure what caused or what is causing the errors but the plug-in would make for an interesting addition allowing Hal to really HAVE a knowledge of time events.
Something to ponder and perhaps examine a bit more thoroughly....