The intensity between local time and UTC time is based on the offset specified as the number of milliseconds.
http://es5.github.com/#x15.9.1.7 says
15.9.1.7 Setting the local time zone
, ECMAScript . - LocalTZA , , UTC . LocalTZA . LocalTZA , .
, , http://bugs.python.org/issue5288 API, , :
Olson ( UNIX Mac OS X) , ( , GMT).
, getUTCMillis .