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POJoda time week calculation reasoning
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copied!<p>The code below demonstrates the problematic joda-time implementation of week calculation. This behavior is not a bug but a design decision <a href="https://stackoverflow.com/questions/1801907/joda-time-first-day-of-week/1808242#1808242">Joda-Time uses the ISO standard Monday to Sunday week.</a> (perhaps it <em>should</em> be a bug?)</p> <p>Given a date I need to calculate the week number, this calculation must be i18n in nature. Meaning <strong>I must</strong> take into consideration the correct week numbering based on the regional settings of the user.</p> <p>The demo code below shows wrong calculation by Joda-Time and correct calculation by the JDK, in the application we try to stick with Joda-Time being a superior solution for date manipulations. So, should I be mixing the two Time calculation libraries? I would obviously prefer not to, is this even a safe thing to do or would I come into corner cases (having experience with Date, Calendar I know for a fact that this is a painful issue for Java).</p> <p>Bottom line: What is the recommended best-practice for the described requirement?</p> <h2>Problem demonstration code</h2> <p>Please see this <a href="http://www.timeanddate.com/calendar/custom.html?year=2009&country=34&cols=0&wno=1&cdt=1&typ=0&display=3&df=1" rel="nofollow noreferrer">online calendar displaying week numbers</a> for correct week calculation example.</p> <pre><code>public class JodaTest { static DateTimeFormatter formatter = DateTimeFormat.forPattern("ww yyyy"); static SimpleDateFormat jdkFormatter = new SimpleDateFormat("ww yyyy"); public static void main(String[] args) { DateTime time = new DateTime(/*year*/2009, /*monthOfYear*/12, /*dayOfMonth*/6, /*hourOfDay*/23, /*minuteOfHour*/0, /*secondOfMinute*/0, /*millisOfSecond*/0); StringBuilder buffer = new StringBuilder() .append("Testing date ").append(time.toString()).append("\n") .append("Joda-Time timezone is ").append(DateTimeZone.getDefault()).append(" yet joda wrongly thinks week is ").append(formatter.print(time)).append("\n") .append("JDK timezone is ").append(TimeZone.getDefault().getID()).append(" yet jdk rightfully thinks week is ").append(jdkFormatter.format(time.toDate())).append(" (jdk got it right ?!?!)"); System.out.println(buffer.toString()); } } </code></pre> <p>Output:</p> <pre><code>Testing date 2009-12-06T23:00:00.000+02:00 Joda-Time timezone is Asia/Jerusalem yet joda wrongly thinks week is 49 2009 JDK time zone is Asia/Jerusalem yet jdk rightfully thinks week is 50 2009 (jdk got it right ?!?!) </code></pre>

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