markdown-it demo

clear permalink

* `getDatePeriodString(long startMillis, long endMillis)` → 回傳 `-P1Y2M3D`
* `getTimeDurationString(long startMillis, long endMillis)` → 回傳 `PT4H5M6S`

> 💡 兩者都會根據毫秒時間戳輸入，自動處理正負順序，只計算到秒，並保留 `-` 號表示反向差距。

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### ✅ 完整 Java 程式碼

```java
import java.time.*;

public class Iso8601DateTimeDiff {

// 回傳年月日部分，例如 P1Y2M3D 或 -P1Y2M3D
    public static String getDatePeriodString(long startMillis, long endMillis) {
        boolean isNegative = endMillis < startMillis;

Instant startInstant = Instant.ofEpochMilli(Math.min(startMillis, endMillis));
        Instant endInstant = Instant.ofEpochMilli(Math.max(startMillis, endMillis));

ZonedDateTime start = startInstant.atZone(ZoneOffset.UTC);
        ZonedDateTime end = endInstant.atZone(ZoneOffset.UTC);

Period period = Period.between(start.toLocalDate(), end.toLocalDate());

StringBuilder sb = new StringBuilder();
        if (isNegative) sb.append("-");
        sb.append(period.toString().replaceAll("-", ""));
        return sb.toString();
    }

// 回傳時間部分，例如 PT4H5M6S 或 -PT4H5M6S（不含毫秒）
    public static String getTimeDurationString(long startMillis, long endMillis) {
        boolean isNegative = endMillis < startMillis;

Instant startInstant = Instant.ofEpochMilli(Math.min(startMillis, endMillis));
        Instant endInstant = Instant.ofEpochMilli(Math.max(startMillis, endMillis));

ZonedDateTime start = startInstant.atZone(ZoneOffset.UTC);
        ZonedDateTime end = endInstant.atZone(ZoneOffset.UTC);

Period period = Period.between(start.toLocalDate(), end.toLocalDate());
        ZonedDateTime dateAlignedStart = start.plus(period);
        Duration duration = Duration.between(dateAlignedStart, end);

StringBuilder sb = new StringBuilder();
        if (isNegative) sb.append("-");
        sb.append(duration.toString().replaceAll("-", ""));
        return sb.toString();
    }

// 測試
    public static void main(String[] args) {
        long start = Instant.parse("2022-01-01T08:00:00.000Z").toEpochMilli();
        long end = Instant.parse("2023-03-04T12:05:06.000Z").toEpochMilli();

System.out.println(getDatePeriodString(start, end));  // P1Y2M3D
        System.out.println(getTimeDurationString(start, end)); // PT4H5M6S

// 測試反向差距
        System.out.println(getDatePeriodString(end, start));  // -P1Y2M3D
        System.out.println(getTimeDurationString(end, start)); // -PT4H5M6S
    }
}
```

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### ✅ 特點

| 功能                         | 支援 |
| -------------------------- | -- |
| 接收毫秒 timestamp (`long`)    | ✅  |
| 支援正向與反向輸出（加 `-`）           | ✅  |
| 獨立輸出 `Period` / `Duration` | ✅  |
| 精度為「秒」，不含毫秒                | ✅  |

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