This AppleScript moves the selected messages to the specified archive mailbox. You must make sure the mailbox exists; the script doesn't check for its existence.

annual-archive-script

-- This script moves messages to a mailbox for the current year
-- Set some default values to be used later in the script
property theMailbox : "Archive"

-- Handler called when running script from script menu
on run
  tell application "Mail"
		set theSelectedMessages to selection
		if ((count of theSelectedMessages) < 1) then
			beep
			return
		end if
		repeat with theMessage in theSelectedMessages
			if (read status of theMessage) is false then
				set read status of theMessage to true
			end if
			move theMessage to mailbox theMailbox
		end repeat
	end tell
end run