exposing system time zone

[Domenic Denicola]

> Interesting questions in that thread about what to do about time zone changes. An event for time zone changes seems important, but we don't currently have any precedent for standard library events in ECMAScript.

Object.observe change records? A synthetic change event seems perfect for this use case.

(Related, although not what I'm suggesting above: http://amasad.me/2014/03/16/why-im-excited-about-objectobserve "Evented Programming" header.)