If you use the private message XML ticker, it has the time/date stamp in format yyyymmddhhmmss. I don't know if any of these chatterbox clients show you this info, but it should be pretty easy to add.
If this were an option on the web chatterbox, maybe show the date (and maybe time) if not today, otherwise just the time.
btw - the times in the ticker is PerlMonks time.
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