tell application "Address Book"
--ensure you have a person selected, and that they have a custom date entry
set thePeople to item 1 of the selection
set o to custom dates of currentPerson
repeat with a in o
return properties of a --shows the properties of the date we wish to delete
delete a --comment out the above line to reveal the bug: you can't delete the custom date.
(*
--
this is my application: the address book has dozens of contacts with 4-6 custom dates with the year seat to "02" thanks to an interaction with iSync
if year of (get value of a) < 1900 then
delete a
end if
*)
end repeat
end tell