How do I calculate the difference in days between two ISO8601 dates with Freemarker?
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I have an object in Freemarker which has dates in ISO8601 format (e.g. `2012-02-01T13:01:02+0000`), how would I go about working out the difference in days between it and now?

In other non-Java scenarios I'd reformat it as a unix timestamp and do the maths (like the `distance_of_time_in_words` functions in RoR or Symfony), however as far as I can see, Freemarker is unable to turn a  ISO8601 timestamp into unix timestamp.

And yes, I realise the template layer probably isn't the right place to be doing this kind of thing, but needs must etc.