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POJava - convert current date into UTC and UTC in any TimeZone
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copied!<p>I need two things:</p> <ol> <li><p>convert current time into UTC (so I can store date in UTC format) --> <strong>result = java.util.Date.</strong></p></li> <li><p>convert loaded date (UTC format) into any TimeZone --> <strong>result = java.util.Date or milliseconds</strong>.</p></li> </ol> <p>For both points bear daylight in mind.</p> <p>1) I found following on stackoverflow:</p> <pre><code>Calendar c = Calendar.getInstance(); System.out.println("current: "+c.getTime()); TimeZone z = c.getTimeZone(); int offset = z.getRawOffset(); if(z.inDaylightTime(new Date())){ offset = offset + z.getDSTSavings(); } int offsetHrs = offset / 1000 / 60 / 60; int offsetMins = offset / 1000 / 60 % 60; System.out.println("offset: " + offsetHrs); System.out.println("offset: " + offsetMins); c.add(Calendar.HOUR_OF_DAY, (-offsetHrs)); c.add(Calendar.MINUTE, (-offsetMins)); System.out.println("GMT Time: "+c.getTime()); </code></pre> <p>--> result equals UTC?</p> <p>2)</p> <pre><code>public static long getTimeMillisFromTimeZone(long utcTimeMillis, String timeZoneId) { System.out.println("input millis: " + utcTimeMillis); Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC")); calendar.setTimeInMillis(utcTimeMillis); TimeZone fromTimeZone = calendar.getTimeZone(); TimeZone toTimeZone = TimeZone.getTimeZone(timeZoneId); calendar.setTimeZone(fromTimeZone); calendar.add(Calendar.MILLISECOND, fromTimeZone.getRawOffset() * -1); if (fromTimeZone.inDaylightTime(calendar.getTime())) { calendar.add(Calendar.MILLISECOND, calendar.getTimeZone() .getDSTSavings() * -1); } calendar.add(Calendar.MILLISECOND, toTimeZone.getRawOffset()); if (toTimeZone.inDaylightTime(calendar.getTime())) { calendar.add(Calendar.MILLISECOND, toTimeZone.getDSTSavings()); } System.out.println(calendar.getTime()); System.out.println("output millis: " + calendar.getTime().getTime()); return calendar.getTime().getTime(); } </code></pre> <p>--> I got a problem there --> lost 1h!</p> <p>In my example I stored a Date from TimeZone "Europe/Vienna" (using daylight) into database as utc. Europa/Vienna --> 10:00 UTC --> 09:00</p> <p>Now I want to convert this UTC (09:00) into "Europe/Vienna" and I get: 09:00 = I lost an hour..</p>

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