FYI.... although I remain a +1 on KISS and emitting "infinity", for
those of you still yearning after a standards-based implementation,
there is a StackOverflow post which hints at sections 3.5 and 3.7 of
ISO8601:2004.
Unfortunatley I can't find a link to an ISO8601:2004 text, so you'll
have to make do with the SO quoted extracts instead....
http://stackoverflow.com/questions/11408249/how-do-you-represent-forever-infinitely-in-the-future-in-iso8601