将儒略日转换为即时

将儒略日转换为即时

这是使用新的Java 8类的解决方案：

public class JulianDay {    private static final double NANOS_PER_DAY = 24.0 * 60.0 * 60.0 * 1000000000.0;    // Calculate Instants for some epochs as defined in Wikipedia.    public static final Instant REDUCED_JD = ZonedDateTime.of(1858, 11, 16, 12, 0, 0, 0, ZoneOffset.UTC).toInstant();    public static final Instant MODIFIED_JD = ZonedDateTime.of(1858, 11, 17, 0, 0, 0, 0, ZoneOffset.UTC).toInstant();    public static final Instant JULIAN_DATE = REDUCED_JD.minus(2400000, ChronoUnit.DAYS);    private final Instant epoch;    public JulianDay(Instant epoch) {        super();        this.epoch = epoch;    }    public Instant toInstant(double day) {        long l = (long) day;        return epoch     .plus(l, ChronoUnit.DAYS)     .plusNanos(Math.round((day - l) * NANOS_PER_DAY));    }    public static void main(String[] args) {        // Use the example values from Wikipedia for 2015-09-07 13:21 UTC.        System.out.println(new JulianDay(REDUCED_JD).toInstant(57273.05625));        // Output: 2015-09-07T13:21:00.000000126Z        System.out.println(new JulianDay(MODIFIED_JD).toInstant(57272.55625));        // Output: 2015-09-07T13:21:00.000000126Z        System.out.println(new JulianDay(JULIAN_DATE).toInstant(2457273.05625));        // Output: 2015-09-07T13:20:59.999991953Z    }}

关于

JulianFields

询问的对象，可以定义一个自定义格式器，如下所示：

DateTimeFormatter formatter = new DateTimeFormatterBuilder()    .appendValue(JulianFields.MODIFIED_JULIAN_DAY)    .toFormatter().withZone(ZoneOffset.UTC);

不幸的是，它不支持几天的时间：

System.out.println(formatter.format(Instant.now())); // Output: 57249System.out.println(LocalDate.from(formatter.parse("57249"))); // Output: 2015-08-15