@CobaltVelvet I prefer RFC 3339. 1) The ISO 8601 standard is not freely accessible 2) It is too complicated, with too many variants (unlike what many people say, alphabetic sorting is not time sorting with ISO 8601 in full)
@bortzmeyer
Re: 1) Is http://www.loc.gov/standards/datetime/iso-tc154-wg5_n0039_iso_wd_8601-2_2016-02-16.pdf not good enough? For that matter, ISO language (C/C++ etc.) standards are not "freely accessible" either, though they are essentially interchangeable with their last working drafts, which are. Standards are for implementers anyway, users are normally better off with secondary documentation (e.g. in the case of ISO 8601, Wikipedia).
RFCs are nice though, and 3339 is an ISO 8601 profile as @CobaltVelvet pointed out.
@ntk @CobaltVelvet As you said, it's a draft. And you cannot even redistribute it.
@bortzmeyer yeah RFC 3339 was sort of implicitly included. It's good too.
At least it's not RFC 2822 or any country-specific unspecified format.