Thanks, Sudhir. I didn't think to search the archives because it wasn't really an XWiki problem. I don't know why it didn't occur to me that if I posted it here, someone else might have - as witness the 'off-topic' caveat when you did. I'm more than fuddled by this. I've found something that works, but I can't begin to explain why. To date, here is how things have fallen out since I sent my note and before reading your reply: First, I tried quoting the 'T', as you suggest, having found this example in the Javadoc for java.text.DateFormat earlier. This satisfied SimpleDateFormat (Duh!, right? SimpleDateFormat.compile doesn't care what's quoted...), and produced identical XML output to the unquoted 'T' which had satisfied the RSS reader, but now failed, producing an invalid-date indication in the displayed date field. If I were a drinking man, I might start thinking of reaching for the bottle. Next, I hit on the idea (for no good reason I can think of; call it "divine inspiration" - or in shorter form: "despiration") of calling $xwiki.formatDate on the Date object, specifying no format so as to use the default from the XWiki preferences (which, I suspect, is exactly how the string version of the element is created, at least when it's an XWiki Object field). This produces XML output identical to the original format that was rejected by the RSS reader, but which is now accepted and reformatted correctly. If I were a drinking man, by this time I'd be singing off key and making lewd suggestions to any remotely desirable lamppost that crossed my path... brain[sic]