mde/timezone-js

Incorrect time transition moment

Closed this issue · 1 comments

maxnikulin commented

Time transition may happen at the wrong moment.
I noticed the issue for the Asia/Novosibirsk timezone
on 20 Oct 2014. TimezoneJS shows transition
a bit later than 9:00 AM instead of precisely at 2:00 AM.
It does not matter if the script runs in Firefox
that respects time transitions history
or in Chromium that follows ECMAScript standard.
This time transition is not a regular DST transition.
Browsers were running in the same Asia/Novosibirsk timezone.

Firefox:

...
timestamp     native Date         timestampJS.Date
...
1414262700    01:45:00 GMT+0700 (NOVT)    1:45 AM    
1414263600    01:00:00 GMT+0600 (NOVT)    2:00 AM    <-
1414264500    01:15:00 GMT+0600 (NOVT)    2:15 AM    
...
1414288800    08:00:00 GMT+0600 (NOVT)    9:00 AM    
1414289700    08:15:00 GMT+0600 (NOVT)    8:15 AM    <-
1414290600    08:30:00 GMT+0600 (NOVT)    8:30 AM    
...

Chromium

...
1414262700    00:45:00 GMT+0600 (NOVT)    1:45 AM    
1414263600    01:00:00 GMT+0600 (NOVT)    2:00 AM    
1414264500    01:15:00 GMT+0600 (NOVT)    2:15 AM    
...
1414288800    08:00:00 GMT+0600 (NOVT)    9:00 AM    
1414289700    08:15:00 GMT+0600 (NOVT)    8:15 AM    <-
1414290600    08:30:00 GMT+0600 (NOVT)    8:30 AM    
...

<!DOCTYPE HTML>
<html>
<head>
  <meta charset="UTF-8">
  <title>Timezone-js time transition</title>
  <script type="text/javascript"
     src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
  <script type="text/javascript" src="timezone-js/src/date.js"></script>
  <script type="text/javascript">
  //<!--
    timezoneJS.timezone.zoneFileBasePath = 'tz';
  //-->
  </script>
</head>
<body>
<h1><a href="https://github.com/mde/timezone-js">Timezone-js</a> time transition</h1>
<pre id="result"></pre>
<script>//<!--

var testTz = "Asia/Novosibirsk";
var testTimestamp = 1414263600;

function getTimes(startTimestamp, duration, step) {
  step = step || 15*60;
  var result = "timestamp     native Date         timestampJS.Date";
  var nativePrev = { hours: 0, minutes: 0 };
  var tzjsPrev = { hours: 0, minutes: 0 };
  for (var dt = 0; dt < duration; dt += step) {
    var t = (startTimestamp + dt)*1000;
    var nativeDate = new Date(t);
    var tzjsDate = new timezoneJS.Date(t, testTz);
    var nativeBack = nativeDate.getHours() < nativePrev.hours || (
      nativeDate.getHours() === nativePrev.hours
      && nativeDate.getMinutes() < nativePrev.minutes
    );
    var tzjsBack = tzjsDate.getHours() < tzjsPrev.hours || (
      tzjsDate.getHours() === tzjsPrev.hours
      && tzjsDate.getMinutes() < tzjsPrev.minutes
    );
    result += "\n" + [
      (t/1000),
      nativeDate.toTimeString(),
      tzjsDate.toTimeString(),
      nativeBack || tzjsBack ? "<-" : null
    ].join("    ");
    nativePrev.hours = nativeDate.getHours();
    nativePrev.minutes = nativeDate.getMinutes();
    tzjsPrev.hours = tzjsDate.getHours();
    tzjsPrev.minutes = tzjsDate.getMinutes();
  }
  return result;
}

document.getElementById("result").innerHTML =
  getTimes(testTimestamp - 2*3600, 10*3600);
//--></script>
</body>
</html>
mde commented

This library is no longer maintained, and this repo is here only for historical interest.