在Java中将本地时间戳转换为UTC时间戳

2022-01-13 00:00:00 datetime timestamp timezone java

我有一个毫秒-since-local-epoch 时间戳，我想将它转换为毫秒-since-UTC-epoch 时间戳.快速浏览一下文档，看起来像这样可以工作:

I have a milliseconds-since-local-epoch timestamp that I'd like to convert into a milliseconds-since-UTC-epoch timestamp. From a quick glance through the docs it looks like something like this would work:

int offset = TimeZone.getDefault().getRawOffset();
long newTime = oldTime - offset;

有没有更好的方法来做到这一点?

Is there a better way to do this?

推荐答案

使用 Calendar 获取本地 Epoch 的偏移量，然后将其添加到本地 epoch 时间戳.

Use a Calendar to get what the offset was at the local Epoch, then add that to the local-epoch timestamp.

public static long getLocalToUtcDelta() {
    Calendar local = Calendar.getInstance();
    local.clear();
    local.set(1970, Calendar.JANUARY, 1, 0, 0, 0);
    return local.getTimeInMillis();
}

public static long converLocalTimeToUtcTime(long timeSinceLocalEpoch) {
    return timeSinceLocalEpoch + getLocalToUtcDelta();
}

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