java - 如何以秒为单位获取当前的 UTC 时间

Question

我有一个应用程序，它需要以秒为单位比较时间。

我想知道如何以秒为单位获取当前的 UTC 时间。

有人可以发布一个示例，我们如何在 Java 中做到这一点？

Answer 1

您可以使用它来获取时区传递您想要时间回到的时区

Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("UTC")); 

然后你可以在日历对象上调用任何你想要的东西

System.out.println(cal.get(Calendar.YEAR));
System.out.println(cal.get(Calendar.HOUR));
System.out.println(cal.get(Calendar.HOUR_OF_DAY));
System.out.println(cal.get(Calendar.MINUTE));

下面的示例在几秒钟内比较两个日历

Calendar cal1 = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
Calendar cal2 = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

// Set the dates for calendars
cal1.set(2011, 1, 1);
cal2.set(2011, 2, 2);

// Get the represented date in milliseconds as a long
long milis1 = cal1.getTimeInMillis();
long milis2 = cal2.getTimeInMillis();

// Calculate difference in milliseconds
long diff = milis2 - milis1;

// Calculate difference in seconds
long diffSecs = diff / 1000;

System.out.println("In seconds: " + diffSecs + " seconds");

Answer 2

System.currentTimeMillis()

Answer 3

Joda让一切变得简单

import org.joda.time.ReadableInstant;
import org.joda.time.DateTime;

import static org.joda.time.DateTimeZone.UTC;
import static org.joda.time.Seconds.secondsBetween;

...

ReadableInstant start = new DateTime("2011-01-01", UTC);
ReadableInstant end = new DateTime("2011-02-02", UTC);

int secondsDifference = secondsBetween(start, end).getSeconds();

Answer 4

 public static  long getUtcTime(long time) {
    System.out.println("Time="+time);
     SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
       Date dbefore=new Date(time);
       System.out.println("Date before conversion="+format.format(dbefore));
      Calendar c = Calendar.getInstance();
       c.setTimeInMillis(time);
          TimeZone timezone = c.getTimeZone();
        int offset = timezone.getRawOffset();
        if(timezone.inDaylightTime(new Date())){
            offset = offset + timezone.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("Date after conversion: "+format.format(c.getTime()));
      System.out.println("Time converted="+c.getTime().getTime());
         return c.getTime().getTime();


    }

Answer 5

以秒为单位获取当前 UTC 时间（从1.5开始）：

TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis())

根据Javadoc：

http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/System.html#currentTimeMillis

回报：

当前时间与 UTC 1970 年 1 月 1 日午夜之间的差异，以毫秒为单位。

Answer 6

要将日期存储为整数而不是长整数，您可以除以 1000 并可选择减去另一个日期，例如 2019 年 1 月 1 日：

private int getUTC()
{
    Calendar cal1 = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
    cal1.set(2019, 1, 1);
    long millis1 = cal1.getTimeInMillis();

    //Current date in milliseconds
    long millis2 = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis());

    // Calculate difference in seconds
    long diff = millis2 - millis1;
    return (int)(diff / 1000);
}

Answer 7

这有效：

    Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
    GregorianCalendar gregorianCalendar = new GregorianCalendar
    (
        calendar.get(Calendar.YEAR),
        calendar.get(Calendar.MONTH),
        calendar.get(Calendar.DAY_OF_MONTH),
        calendar.get(Calendar.HOUR_OF_DAY),
        calendar.get(Calendar.MINUTE),
        calendar.get(Calendar.SECOND)
    );
    return gregorianCalendar.getTime();