Safari has a bug on parsing Date when both its time and timezone are negative value.

check-date-bug.js

/**
 * Safari has a bug on parsing Date when both its time and timezone are negative value.
 * 
 * @author @kawanet
 * @license MIT
 * @see https://github.com/kawanet/timestamp-nano/blob/master/test/52.timezone.js
 * @see https://gist.github.com/kawanet/4947237d84ba6efb16183ffcc23e982a
 */

function checkDateBug() {
  var date = +new Date("1969-12-31T23:59:59.999-01:00");
  return date % 1000 !== 999;
}

if ("undefined" !== typeof module) module.exports = checkDateBug;

Safari looks to have a JavaScript bug to give 1 millisecond difference on parsing Date string before 1970 on the Western Hemisphere.

This gist above could detect the environment which has the bug as below:

new Date("1969-12-31T23:59:59.999+01:00").toJSON();
// OK! => "1969-12-31T22:59:59.999Z"

new Date("1969-12-31T23:59:59.999-01:00").toJSON();
// NG! => "1970-01-01T00:59:59.998Z"

The number of (milli)seconds must be 59.999 but NOT 59.998. It gives one millisecond inaccuracy.