I am trying to retrieve a converted "hour" integer for a user's time zone with GMT unix time. My code works SOME of the time, though for example, it was 9:00pm on the east coast and getting a 0 for the hour. can anyone help?

我正在尝试检索具有GMT Unix时间的用户时区的转换后的“小时”整数。我的代码有时是有效的，但例如，现在是东海岸晚上9点，一小时得了0分。有谁能帮忙吗？

long l = Long.parseLong(oslist.get(position).get("hour"));

                Calendar calendar = Calendar.getInstance();
                calendar.setTimeInMillis(l);
                calendar.setTimeInMillis(l * 1000);
                calendar.setTimeZone(TimeZone.getDefault());

                int hour = calendar.get(Calendar.HOUR);
                Log.v("TIME:", ""+hour);

You don't need to set the time zone - it's default by default, as it were. And calling setTimeInMillis twice is pointless. So just:

您不需要设置时区--可以说，这是默认设置。并且两次调用setTimeInMillis是没有意义的。所以只要：

Calendar calendar = calendar.getInstance();
calendar.setTimeInMillis(unixTimestamp * 1000L);
int hour = calendar.get(Calendar.HOUR);

... should be absolutely fine. If it's not, then going via string representations as suggested by other answers isn't going to help.

..。应该完全没问题。如果不是，那么像其他答案所建议的那样通过字符串表示将不会有任何帮助。

If that's giving 0 when it's 9pm on the East Coast, that suggests the default time zone is not one representing the East Coast. I suggest you diagnose that first:

如果当东海岸是晚上9点的时候是0，那就表明默认时区不代表东海岸。我建议你先诊断一下：

System.out.println(TimeZone.getDefault().getID());
// Just in case the ID is misleading, what's the standard offset for this zone?
System.out.println(TimeZone.getDefault().getRawOffset());

java.time

The java.util date-time API and their corresponding parsing/formatting type, SimpleDateFormat are outdated and error-prone. In March 2014, the modern Date-Time API supplanted this API. Since then, it has been strongly recommended to switch to java.time, the modern date-time API.

Util Date-Time API及其对应的解析/格式化类型SimpleDateFormat已经过时且容易出错。2014年3月，现代的Date-Time API取代了此API。从那时起，强烈建议改用现代的日期-时间API--java.time。

Solution using java.time API:

使用java.time API的解决方案：

You can use Instant#ofEpochSecond to get the Instant corresponding to your given Unix timestamp. Next, convert the Instant to a ZonedDateTime at the required timezone and then you can get individual time units (e.g. hour) out of this ZonedDateTime.

您可以使用Instant#of EpochSecond来获取与您给定的Unix时间戳对应的Instant。接下来，将Instant转换为所需时区的ZonedDateTime，然后您可以从该ZonedDateTime中获得单独的时间单位(例如小时)。

// e.g. a Unix timestamp representing 9:00pm on 10-Sep-2023 in New York
long epochSeconds = 1694394000L;
Instant instant = Instant.ofEpochSecond(epochSeconds);
ZonedDateTime zdt = instant.atZone(ZoneId.of("America/New_York"));
System.out.println(zdt);
System.out.println(zdt.getHour());

Output:

产出：

2023-09-10T21:00-04:00[America/New_York]
21

Online Demo

在线演示

Learn more about the modern date-time API from Trail: Date Time

从Trail：Date Time了解有关现代Date-Time API的更多信息

Also, if you need the timezone itself, see Class SimpleDateFormat. Specifically the z and Z formats.

此外，如果需要时区本身，请参见类SimpleDateFormat。具体地说，是z和Z格式。

Try this:

试试这个：

long l = Long.parseLong(oslist.get(position).get("hour"));

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(l);
    calendar.setTimeInMillis(l * 1000);
    Date date = calendar.getTime(); //current date and time in UTC
    SimpleDateFormat df = new SimpleDateFormat("HH"); //HH = 0-23 hours
    df.setTimeZone(TimeZone.getDefault()); //format in given timezone

    String hourStringValue = df.format(date);
    int hourIntValue = Integer.parseInt(hourStringValue);