ServiceStack/ServiceStack.Text — pull request #116 by PaulECoyote (2012-04-26 15:38:36+00:00)
Title: ISO 8601 (Nullable)TimeSpans to be (de)serialised from json

Added support for (Nullable)TimeSpans to be (de)serialised from json in ISO 8601.

Browser support isn't widely available for that format yet - but I'm not sure the current .net outputted timespan is either.