I was particularly interested in the Virtualtag that expresses "Released: <CustomDateField?>/<Year> (yyyy)"
That's my RH grouping header
It uses a custom tag - Release Date Sort - in the format YYYYMMDD that I use a virtual tag to convert to the format DD Mon YYYY for display.
It removes DD and DD Mon if they are unknown (00).
Hold onto something, cause it's a big formula

Released: $If($Right(<Release Date Sort>,4)=0000,<YYYY>,$If($Right($Right(<Release Date Sort>,4),2)=00,$If($Left($Right(<Release Date Sort>,4),2)=01,"Jan "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=02,"Feb "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=03,"Mar "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=04,"Apr "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=05,"May "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=06,"Jun "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=07,"Jul "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=08,"Aug "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=09,"Sep "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=10,"Oct "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=11,"Nov "<YYYY>,"Dec "<YYYY>))))))))))),$If($Left($Right($Right(<Release Date Sort>,4),2),1)=0,$Right($Right(<Release Date Sort>,4),1),$Right($Right(<Release Date Sort>,4),2))" "$If($Left($Right(<Release Date Sort>,4),2)=01,"Jan "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=02,"Feb "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=03,"Mar "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=04,"Apr "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=05,"May "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=06,"Jun "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=07,"Jul "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=08,"Aug "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=09,"Sep "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=10,"Oct "<YYYY>,$If($Left($Right(<Release Date Sort>,4),2)=11,"Nov "<YYYY>,"Dec "<YYYY>)))))))))))))