JSON text ([RFC 4627](http://www.ietf.org/rfc/rfc4627.txt?number=4627)) has unambigious representation of objects, arrays, strings, numbers, Boolean values (literally `true` or `false`) and `null`. However, it has nothing defined for representing time information like date and time of day, which is very common in applications. What are the current methods in use to represent time in JSON given the constraints and grammar laid out in [RFC 4627](http://www.ietf.org/rfc/rfc4627.txt?number=4627)?

Note to respondents: The purpose of this question is to document the various methods known to be in circulation along with examples and relative pros and cons (ideally from field experience).