ZonedDateTime.java

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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
 *
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are met:
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 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
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package java.time;

import static java.time.temporal.ChronoField.INSTANT_SECONDS;
import static java.time.temporal.ChronoField.NANO_OF_SECOND;
import static java.time.temporal.ChronoField.OFFSET_SECONDS;

import java.io.DataOutput;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.time.chrono.ChronoZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAccessor;
import java.time.temporal.TemporalAdjuster;
import java.time.temporal.TemporalAmount;
import java.time.temporal.TemporalField;
import java.time.temporal.TemporalQueries;
import java.time.temporal.TemporalQuery;
import java.time.temporal.TemporalUnit;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.time.temporal.ValueRange;
import java.time.zone.ZoneOffsetTransition;
import java.time.zone.ZoneRules;
import java.util.List;
import java.util.Objects;

import jdk.internal.util.DateTimeHelper;

/**
 * A date-time with a time-zone in the ISO-8601 calendar system,
 * such as {@code 2007-12-03T10:15:30+01:00 Europe/Paris}.
 * <p>
 * {@code ZonedDateTime} is an immutable representation of a date-time with a time-zone.
 * This class stores all date and time fields, to a precision of nanoseconds,
 * and a time-zone, with a zone offset used to handle ambiguous local date-times.
 * For example, the value
 * "2nd October 2007 at 13:45.30.123456789 +02:00 in the Europe/Paris time-zone"
 * can be stored in a {@code ZonedDateTime}.
 * <p>
 * This class handles conversion from the local time-line of {@code LocalDateTime}
 * to the instant time-line of {@code Instant}.
 * The difference between the two time-lines is the offset from UTC/Greenwich,
 * represented by a {@code ZoneOffset}.
 * <p>
 * Converting between the two time-lines involves calculating the offset using the
 * {@link ZoneRules rules} accessed from the {@code ZoneId}.
 * Obtaining the offset for an instant is simple, as there is exactly one valid
 * offset for each instant. By contrast, obtaining the offset for a local date-time
 * is not straightforward. There are three cases:
 * <ul>
 * <li>Normal, with one valid offset. For the vast majority of the year, the normal
 *  case applies, where there is a single valid offset for the local date-time.</li>
 * <li>Gap, with zero valid offsets. This is when clocks jump forward typically
 *  due to the spring daylight savings change from "winter" to "summer".
 *  In a gap there are local date-time values with no valid offset.</li>
 * <li>Overlap, with two valid offsets. This is when clocks are set back typically
 *  due to the autumn daylight savings change from "summer" to "winter".
 *  In an overlap there are local date-time values with two valid offsets.</li>
 * </ul>
 * <p>
 * Any method that converts directly or implicitly from a local date-time to an
 * instant by obtaining the offset has the potential to be complicated.
 * <p>
 * For Gaps, the general strategy is that if the local date-time falls in the
 * middle of a Gap, then the resulting zoned date-time will have a local date-time
 * shifted forwards by the length of the Gap, resulting in a date-time in the later
 * offset, typically "summer" time.
 * <p>
 * For Overlaps, the general strategy is that if the local date-time falls in the
 * middle of an Overlap, then the previous offset will be retained. If there is no
 * previous offset, or the previous offset is invalid, then the earlier offset is
 * used, typically "summer" time.. Two additional methods,
 * {@link #withEarlierOffsetAtOverlap()} and {@link #withLaterOffsetAtOverlap()},
 * help manage the case of an overlap.
 * <p>
 * In terms of design, this class should be viewed primarily as the combination
 * of a {@code LocalDateTime} and a {@code ZoneId}. The {@code ZoneOffset} is
 * a vital, but secondary, piece of information, used to ensure that the class
 * represents an instant, especially during a daylight savings overlap.
 * <p>
 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 * class; programmers should treat instances that are
 * {@linkplain #equals(Object) equal} as interchangeable and should not
 * use instances for synchronization, or unpredictable behavior may
 * occur. For example, in a future release, synchronization may fail.
 * The {@code equals} method should be used for comparisons.
 *
 * @implSpec
 * A {@code ZonedDateTime} holds state equivalent to three separate objects,
 * a {@code LocalDateTime}, a {@code ZoneId} and the resolved {@code ZoneOffset}.
 * The offset and local date-time are used to define an instant when necessary.
 * The zone ID is used to obtain the rules for how and when the offset changes.
 * The offset cannot be freely set, as the zone controls which offsets are valid.
 * <p>
 * This class is immutable and thread-safe.
 *
 * @since 1.8
 */
@jdk.internal.ValueBased
public final class ZonedDateTime
        implements Temporal, ChronoZonedDateTime<LocalDate>, Serializable {

    /**
     * Serialization version.
     */
    @java.io.Serial
    private static final long serialVersionUID = -6260982410461394882L;

    /**
     * @serial The local date-time.
     */
    private final LocalDateTime dateTime;
    /**
     * @serial The offset from UTC/Greenwich.
     */
    private final ZoneOffset offset;
    /**
     * @serial The time-zone.
     */
    private final ZoneId zone;

    //-----------------------------------------------------------------------
    /**
     * Obtains the current date-time from the system clock in the default time-zone.
     * <p>
     * This will query the {@link Clock#systemDefaultZone() system clock} in the default
     * time-zone to obtain the current date-time.
     * The zone and offset will be set based on the time-zone in the clock.
     * <p>
     * Using this method will prevent the ability to use an alternate clock for testing
     * because the clock is hard-coded.
     *
     * @return the current date-time using the system clock, not null
     */
    public static ZonedDateTime now() {
        return now(Clock.systemDefaultZone());
    }

    /**
     * Obtains the current date-time from the system clock in the specified time-zone.
     * <p>
     * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current date-time.
     * Specifying the time-zone avoids dependence on the default time-zone.
     * The offset will be calculated from the specified time-zone.
     * <p>
     * Using this method will prevent the ability to use an alternate clock for testing
     * because the clock is hard-coded.
     *
     * @param zone  the zone ID to use, not null
     * @return the current date-time using the system clock, not null
     */
    public static ZonedDateTime now(ZoneId zone) {
        return now(Clock.system(zone));
    }

    /**
     * Obtains the current date-time from the specified clock.
     * <p>
     * This will query the specified clock to obtain the current date-time.
     * The zone and offset will be set based on the time-zone in the clock.
     * <p>
     * Using this method allows the use of an alternate clock for testing.
     * The alternate clock may be introduced using {@link Clock dependency injection}.
     *
     * @param clock  the clock to use, not null
     * @return the current date-time, not null
     */
    public static ZonedDateTime now(Clock clock) {
        Objects.requireNonNull(clock, "clock");
        final Instant now = clock.instant();  // called once
        return ofInstant(now, clock.getZone());
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ZonedDateTime} from a local date and time.
     * <p>
     * This creates a zoned date-time matching the input local date and time as closely as possible.
     * Time-zone rules, such as daylight savings, mean that not every local date-time
     * is valid for the specified zone, thus the local date-time may be adjusted.
     * <p>
     * The local date time and first combined to form a local date-time.
     * The local date-time is then resolved to a single instant on the time-line.
     * This is achieved by finding a valid offset from UTC/Greenwich for the local
     * date-time as defined by the {@link ZoneRules rules} of the zone ID.
     *<p>
     * In most cases, there is only one valid offset for a local date-time.
     * In the case of an overlap, when clocks are set back, there are two valid offsets.
     * This method uses the earlier offset typically corresponding to "summer".
     * <p>
     * In the case of a gap, when clocks jump forward, there is no valid offset.
     * Instead, the local date-time is adjusted to be later by the length of the gap.
     * For a typical one hour daylight savings change, the local date-time will be
     * moved one hour later into the offset typically corresponding to "summer".
     *
     * @param date  the local date, not null
     * @param time  the local time, not null
     * @param zone  the time-zone, not null
     * @return the offset date-time, not null
     */
    public static ZonedDateTime of(LocalDate date, LocalTime time, ZoneId zone) {
        return of(LocalDateTime.of(date, time), zone);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} from a local date-time.
     * <p>
     * This creates a zoned date-time matching the input local date-time as closely as possible.
     * Time-zone rules, such as daylight savings, mean that not every local date-time
     * is valid for the specified zone, thus the local date-time may be adjusted.
     * <p>
     * The local date-time is resolved to a single instant on the time-line.
     * This is achieved by finding a valid offset from UTC/Greenwich for the local
     * date-time as defined by the {@link ZoneRules rules} of the zone ID.
     *<p>
     * In most cases, there is only one valid offset for a local date-time.
     * In the case of an overlap, when clocks are set back, there are two valid offsets.
     * This method uses the earlier offset typically corresponding to "summer".
     * <p>
     * In the case of a gap, when clocks jump forward, there is no valid offset.
     * Instead, the local date-time is adjusted to be later by the length of the gap.
     * For a typical one hour daylight savings change, the local date-time will be
     * moved one hour later into the offset typically corresponding to "summer".
     *
     * @param localDateTime  the local date-time, not null
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     */
    public static ZonedDateTime of(LocalDateTime localDateTime, ZoneId zone) {
        return ofLocal(localDateTime, zone, null);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} from a year, month, day,
     * hour, minute, second, nanosecond and time-zone.
     * <p>
     * This creates a zoned date-time matching the local date-time of the seven
     * specified fields as closely as possible.
     * Time-zone rules, such as daylight savings, mean that not every local date-time
     * is valid for the specified zone, thus the local date-time may be adjusted.
     * <p>
     * The local date-time is resolved to a single instant on the time-line.
     * This is achieved by finding a valid offset from UTC/Greenwich for the local
     * date-time as defined by the {@link ZoneRules rules} of the zone ID.
     *<p>
     * In most cases, there is only one valid offset for a local date-time.
     * In the case of an overlap, when clocks are set back, there are two valid offsets.
     * This method uses the earlier offset typically corresponding to "summer".
     * <p>
     * In the case of a gap, when clocks jump forward, there is no valid offset.
     * Instead, the local date-time is adjusted to be later by the length of the gap.
     * For a typical one hour daylight savings change, the local date-time will be
     * moved one hour later into the offset typically corresponding to "summer".
     * <p>
     * This method exists primarily for writing test cases.
     * Non test-code will typically use other methods to create an offset time.
     * {@code LocalDateTime} has five additional convenience variants of the
     * equivalent factory method taking fewer arguments.
     * They are not provided here to reduce the footprint of the API.
     *
     * @param year  the year to represent, from MIN_YEAR to MAX_YEAR
     * @param month  the month-of-year to represent, from 1 (January) to 12 (December)
     * @param dayOfMonth  the day-of-month to represent, from 1 to 31
     * @param hour  the hour-of-day to represent, from 0 to 23
     * @param minute  the minute-of-hour to represent, from 0 to 59
     * @param second  the second-of-minute to represent, from 0 to 59
     * @param nanoOfSecond  the nano-of-second to represent, from 0 to 999,999,999
     * @param zone  the time-zone, not null
     * @return the offset date-time, not null
     * @throws DateTimeException if the value of any field is out of range, or
     *  if the day-of-month is invalid for the month-year
     */
    public static ZonedDateTime of(
            int year, int month, int dayOfMonth,
            int hour, int minute, int second, int nanoOfSecond, ZoneId zone) {
        LocalDateTime dt = LocalDateTime.of(year, month, dayOfMonth, hour, minute, second, nanoOfSecond);
        return ofLocal(dt, zone, null);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} from a local date-time
     * using the preferred offset if possible.
     * <p>
     * The local date-time is resolved to a single instant on the time-line.
     * This is achieved by finding a valid offset from UTC/Greenwich for the local
     * date-time as defined by the {@link ZoneRules rules} of the zone ID.
     *<p>
     * In most cases, there is only one valid offset for a local date-time.
     * In the case of an overlap, where clocks are set back, there are two valid offsets.
     * If the preferred offset is one of the valid offsets then it is used.
     * Otherwise the earlier valid offset is used, typically corresponding to "summer".
     * <p>
     * In the case of a gap, where clocks jump forward, there is no valid offset.
     * Instead, the local date-time is adjusted to be later by the length of the gap.
     * For a typical one hour daylight savings change, the local date-time will be
     * moved one hour later into the offset typically corresponding to "summer".
     *
     * @param localDateTime  the local date-time, not null
     * @param zone  the time-zone, not null
     * @param preferredOffset  the zone offset, null if no preference
     * @return the zoned date-time, not null
     */
    public static ZonedDateTime ofLocal(LocalDateTime localDateTime, ZoneId zone, ZoneOffset preferredOffset) {
        Objects.requireNonNull(localDateTime, "localDateTime");
        Objects.requireNonNull(zone, "zone");
        if (zone instanceof ZoneOffset) {
            return new ZonedDateTime(localDateTime, (ZoneOffset) zone, zone);
        }
        ZoneRules rules = zone.getRules();
        List<ZoneOffset> validOffsets = rules.getValidOffsets(localDateTime);
        ZoneOffset offset;
        if (validOffsets.size() == 1) {
            offset = validOffsets.get(0);
        } else if (validOffsets.size() == 0) {
            ZoneOffsetTransition trans = rules.getTransition(localDateTime);
            localDateTime = localDateTime.plusSeconds(trans.getDuration().getSeconds());
            offset = trans.getOffsetAfter();
        } else {
            if (preferredOffset != null && validOffsets.contains(preferredOffset)) {
                offset = preferredOffset;
            } else {
                offset = Objects.requireNonNull(validOffsets.get(0), "offset");  // protect against bad ZoneRules
            }
        }
        return new ZonedDateTime(localDateTime, offset, zone);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ZonedDateTime} from an {@code Instant}.
     * <p>
     * This creates a zoned date-time with the same instant as that specified.
     * Calling {@link #toInstant()} will return an instant equal to the one used here.
     * <p>
     * Converting an instant to a zoned date-time is simple as there is only one valid
     * offset for each instant.
     *
     * @param instant  the instant to create the date-time from, not null
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     * @throws DateTimeException if the result exceeds the supported range
     */
    public static ZonedDateTime ofInstant(Instant instant, ZoneId zone) {
        Objects.requireNonNull(instant, "instant");
        Objects.requireNonNull(zone, "zone");
        return create(instant.getEpochSecond(), instant.getNano(), zone);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} from the instant formed by combining
     * the local date-time and offset.
     * <p>
     * This creates a zoned date-time by {@link LocalDateTime#toInstant(ZoneOffset) combining}
     * the {@code LocalDateTime} and {@code ZoneOffset}.
     * This combination uniquely specifies an instant without ambiguity.
     * <p>
     * Converting an instant to a zoned date-time is simple as there is only one valid
     * offset for each instant. If the valid offset is different to the offset specified,
     * then the date-time and offset of the zoned date-time will differ from those specified.
     * <p>
     * If the {@code ZoneId} to be used is a {@code ZoneOffset}, this method is equivalent
     * to {@link #of(LocalDateTime, ZoneId)}.
     *
     * @param localDateTime  the local date-time, not null
     * @param offset  the zone offset, not null
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     */
    public static ZonedDateTime ofInstant(LocalDateTime localDateTime, ZoneOffset offset, ZoneId zone) {
        Objects.requireNonNull(localDateTime, "localDateTime");
        Objects.requireNonNull(offset, "offset");
        Objects.requireNonNull(zone, "zone");
        if (zone.getRules().isValidOffset(localDateTime, offset)) {
            return new ZonedDateTime(localDateTime, offset, zone);
        }
        return create(localDateTime.toEpochSecond(offset), localDateTime.getNano(), zone);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} using seconds from the
     * epoch of 1970-01-01T00:00:00Z.
     *
     * @param epochSecond  the number of seconds from the epoch of 1970-01-01T00:00:00Z
     * @param nanoOfSecond  the nanosecond within the second, from 0 to 999,999,999
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     * @throws DateTimeException if the result exceeds the supported range
     */
    private static ZonedDateTime create(long epochSecond, int nanoOfSecond, ZoneId zone) {
        // nanoOfSecond is in a range that'll not affect epochSecond, validated
        // by LocalDateTime.ofEpochSecond
        ZoneOffset offset = zone.getOffset(epochSecond);
        LocalDateTime ldt = LocalDateTime.ofEpochSecond(epochSecond, nanoOfSecond, offset);
        return new ZonedDateTime(ldt, offset, zone);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ZonedDateTime} strictly validating the
     * combination of local date-time, offset and zone ID.
     * <p>
     * This creates a zoned date-time ensuring that the offset is valid for the
     * local date-time according to the rules of the specified zone.
     * If the offset is invalid, an exception is thrown.
     *
     * @param localDateTime  the local date-time, not null
     * @param offset  the zone offset, not null
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     * @throws DateTimeException if the combination of arguments is invalid
     */
    public static ZonedDateTime ofStrict(LocalDateTime localDateTime, ZoneOffset offset, ZoneId zone) {
        Objects.requireNonNull(localDateTime, "localDateTime");
        Objects.requireNonNull(offset, "offset");
        Objects.requireNonNull(zone, "zone");
        ZoneRules rules = zone.getRules();
        if (rules.isValidOffset(localDateTime, offset) == false) {
            ZoneOffsetTransition trans = rules.getTransition(localDateTime);
            if (trans != null && trans.isGap()) {
                // error message says daylight savings for simplicity
                // even though there are other kinds of gaps
                throw new DateTimeException("LocalDateTime '" + localDateTime +
                        "' does not exist in zone '" + zone +
                        "' due to a gap in the local time-line, typically caused by daylight savings");
            }
            throw new DateTimeException("ZoneOffset '" + offset + "' is not valid for LocalDateTime '" +
                    localDateTime + "' in zone '" + zone + "'");
        }
        return new ZonedDateTime(localDateTime, offset, zone);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} leniently, for advanced use cases,
     * allowing any combination of local date-time, offset and zone ID.
     * <p>
     * This creates a zoned date-time with no checks other than no nulls.
     * This means that the resulting zoned date-time may have an offset that is in conflict
     * with the zone ID.
     * <p>
     * This method is intended for advanced use cases.
     * For example, consider the case where a zoned date-time with valid fields is created
     * and then stored in a database or serialization-based store. At some later point,
     * the object is then re-loaded. However, between those points in time, the government
     * that defined the time-zone has changed the rules, such that the originally stored
     * local date-time now does not occur. This method can be used to create the object
     * in an "invalid" state, despite the change in rules.
     *
     * @param localDateTime  the local date-time, not null
     * @param offset  the zone offset, not null
     * @param zone  the time-zone, not null
     * @return the zoned date-time, not null
     */
    private static ZonedDateTime ofLenient(LocalDateTime localDateTime, ZoneOffset offset, ZoneId zone) {
        Objects.requireNonNull(localDateTime, "localDateTime");
        Objects.requireNonNull(offset, "offset");
        Objects.requireNonNull(zone, "zone");
        if (zone instanceof ZoneOffset && offset.equals(zone) == false) {
            throw new IllegalArgumentException("ZoneId must match ZoneOffset");
        }
        return new ZonedDateTime(localDateTime, offset, zone);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ZonedDateTime} from a temporal object.
     * <p>
     * This obtains a zoned date-time based on the specified temporal.
     * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
     * which this factory converts to an instance of {@code ZonedDateTime}.
     * <p>
     * The conversion will first obtain a {@code ZoneId} from the temporal object,
     * falling back to a {@code ZoneOffset} if necessary. It will then try to obtain
     * an {@code Instant}, falling back to a {@code LocalDateTime} if necessary.
     * The result will be either the combination of {@code ZoneId} or {@code ZoneOffset}
     * with {@code Instant} or {@code LocalDateTime}.
     * Implementations are permitted to perform optimizations such as accessing
     * those fields that are equivalent to the relevant objects.
     * <p>
     * This method matches the signature of the functional interface {@link TemporalQuery}
     * allowing it to be used as a query via method reference, {@code ZonedDateTime::from}.
     *
     * @param temporal  the temporal object to convert, not null
     * @return the zoned date-time, not null
     * @throws DateTimeException if unable to convert to an {@code ZonedDateTime}
     */
    public static ZonedDateTime from(TemporalAccessor temporal) {
        if (temporal instanceof ZonedDateTime) {
            return (ZonedDateTime) temporal;
        }
        try {
            ZoneId zone = ZoneId.from(temporal);
            if (temporal.isSupported(INSTANT_SECONDS)) {
                long epochSecond = temporal.getLong(INSTANT_SECONDS);
                int nanoOfSecond = temporal.get(NANO_OF_SECOND);
                return create(epochSecond, nanoOfSecond, zone);
            } else {
                LocalDate date = LocalDate.from(temporal);
                LocalTime time = LocalTime.from(temporal);
                return of(date, time, zone);
            }
        } catch (DateTimeException ex) {
            throw new DateTimeException("Unable to obtain ZonedDateTime from TemporalAccessor: " +
                    temporal + " of type " + temporal.getClass().getName(), ex);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code ZonedDateTime} from a text string such as
     * {@code 2007-12-03T10:15:30+01:00[Europe/Paris]}.
     * <p>
     * The string must represent a valid date-time and is parsed using
     * {@link java.time.format.DateTimeFormatter#ISO_ZONED_DATE_TIME}.
     *
     * @param text  the text to parse such as "2007-12-03T10:15:30+01:00[Europe/Paris]", not null
     * @return the parsed zoned date-time, not null
     * @throws DateTimeParseException if the text cannot be parsed
     */
    public static ZonedDateTime parse(CharSequence text) {
        return parse(text, DateTimeFormatter.ISO_ZONED_DATE_TIME);
    }

    /**
     * Obtains an instance of {@code ZonedDateTime} from a text string using a specific formatter.
     * <p>
     * The text is parsed using the formatter, returning a date-time.
     *
     * @param text  the text to parse, not null
     * @param formatter  the formatter to use, not null
     * @return the parsed zoned date-time, not null
     * @throws DateTimeParseException if the text cannot be parsed
     */
    public static ZonedDateTime parse(CharSequence text, DateTimeFormatter formatter) {
        Objects.requireNonNull(formatter, "formatter");
        return formatter.parse(text, ZonedDateTime::from);
    }

    //-----------------------------------------------------------------------
    /**
     * Constructor.
     *
     * @param dateTime  the date-time, validated as not null
     * @param offset  the zone offset, validated as not null
     * @param zone  the time-zone, validated as not null
     */
    private ZonedDateTime(LocalDateTime dateTime, ZoneOffset offset, ZoneId zone) {
        this.dateTime = dateTime;
        this.offset = offset;
        this.zone = zone;
    }

    /**
     * Resolves the new local date-time using this zone ID, retaining the offset if possible.
     *
     * @param newDateTime  the new local date-time, not null
     * @return the zoned date-time, not null
     */
    private ZonedDateTime resolveLocal(LocalDateTime newDateTime) {
        return ofLocal(newDateTime, zone, offset);
    }

    /**
     * Resolves the new local date-time using the offset to identify the instant.
     *
     * @param newDateTime  the new local date-time, not null
     * @return the zoned date-time, not null
     */
    private ZonedDateTime resolveInstant(LocalDateTime newDateTime) {
        return ofInstant(newDateTime, offset, zone);
    }

    /**
     * Resolves the offset into this zoned date-time for the with methods.
     * <p>
     * This typically ignores the offset, unless it can be used to switch offset in a DST overlap.
     *
     * @param offset  the offset, not null
     * @return the zoned date-time, not null
     */
    private ZonedDateTime resolveOffset(ZoneOffset offset) {
        if (offset.equals(this.offset) == false && zone.getRules().isValidOffset(dateTime, offset)) {
            return new ZonedDateTime(dateTime, offset, zone);
        }
        return this;
    }

    //-----------------------------------------------------------------------
    /**
     * Checks if the specified field is supported.
     * <p>
     * This checks if this date-time can be queried for the specified field.
     * If false, then calling the {@link #range(TemporalField) range},
     * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)}
     * methods will throw an exception.
     * <p>
     * If the field is a {@link ChronoField} then the query is implemented here.
     * The supported fields are:
     * <ul>
     * <li>{@code NANO_OF_SECOND}
     * <li>{@code NANO_OF_DAY}
     * <li>{@code MICRO_OF_SECOND}
     * <li>{@code MICRO_OF_DAY}
     * <li>{@code MILLI_OF_SECOND}
     * <li>{@code MILLI_OF_DAY}
     * <li>{@code SECOND_OF_MINUTE}
     * <li>{@code SECOND_OF_DAY}
     * <li>{@code MINUTE_OF_HOUR}
     * <li>{@code MINUTE_OF_DAY}
     * <li>{@code HOUR_OF_AMPM}
     * <li>{@code CLOCK_HOUR_OF_AMPM}
     * <li>{@code HOUR_OF_DAY}
     * <li>{@code CLOCK_HOUR_OF_DAY}
     * <li>{@code AMPM_OF_DAY}
     * <li>{@code DAY_OF_WEEK}
     * <li>{@code ALIGNED_DAY_OF_WEEK_IN_MONTH}
     * <li>{@code ALIGNED_DAY_OF_WEEK_IN_YEAR}
     * <li>{@code DAY_OF_MONTH}
     * <li>{@code DAY_OF_YEAR}
     * <li>{@code EPOCH_DAY}
     * <li>{@code ALIGNED_WEEK_OF_MONTH}
     * <li>{@code ALIGNED_WEEK_OF_YEAR}
     * <li>{@code MONTH_OF_YEAR}
     * <li>{@code PROLEPTIC_MONTH}
     * <li>{@code YEAR_OF_ERA}
     * <li>{@code YEAR}
     * <li>{@code ERA}
     * <li>{@code INSTANT_SECONDS}
     * <li>{@code OFFSET_SECONDS}
     * </ul>
     * All other {@code ChronoField} instances will return false.
     * <p>
     * If the field is not a {@code ChronoField}, then the result of this method
     * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
     * passing {@code this} as the argument.
     * Whether the field is supported is determined by the field.
     *
     * @param field  the field to check, null returns false
     * @return true if the field is supported on this date-time, false if not
     */
    @Override
    public boolean isSupported(TemporalField field) {
        return field instanceof ChronoField || (field != null && field.isSupportedBy(this));
    }

    /**
     * Checks if the specified unit is supported.
     * <p>
     * This checks if the specified unit can be added to, or subtracted from, this date-time.
     * If false, then calling the {@link #plus(long, TemporalUnit)} and
     * {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
     * <p>
     * If the unit is a {@link ChronoUnit} then the query is implemented here.
     * The supported units are:
     * <ul>
     * <li>{@code NANOS}
     * <li>{@code MICROS}
     * <li>{@code MILLIS}
     * <li>{@code SECONDS}
     * <li>{@code MINUTES}
     * <li>{@code HOURS}
     * <li>{@code HALF_DAYS}
     * <li>{@code DAYS}
     * <li>{@code WEEKS}
     * <li>{@code MONTHS}
     * <li>{@code YEARS}
     * <li>{@code DECADES}
     * <li>{@code CENTURIES}
     * <li>{@code MILLENNIA}
     * <li>{@code ERAS}
     * </ul>
     * All other {@code ChronoUnit} instances will return false.
     * <p>
     * If the unit is not a {@code ChronoUnit}, then the result of this method
     * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}
     * passing {@code this} as the argument.
     * Whether the unit is supported is determined by the unit.
     *
     * @param unit  the unit to check, null returns false
     * @return true if the unit can be added/subtracted, false if not
     */
    @Override  // override for Javadoc
    public boolean isSupported(TemporalUnit unit) {
        return ChronoZonedDateTime.super.isSupported(unit);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the range of valid values for the specified field.
     * <p>
     * The range object expresses the minimum and maximum valid values for a field.
     * This date-time is used to enhance the accuracy of the returned range.
     * If it is not possible to return the range, because the field is not supported
     * or for some other reason, an exception is thrown.
     * <p>
     * If the field is a {@link ChronoField} then the query is implemented here.
     * The {@link #isSupported(TemporalField) supported fields} will return
     * appropriate range instances.
     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
     * <p>
     * If the field is not a {@code ChronoField}, then the result of this method
     * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
     * passing {@code this} as the argument.
     * Whether the range can be obtained is determined by the field.
     *
     * @param field  the field to query the range for, not null
     * @return the range of valid values for the field, not null
     * @throws DateTimeException if the range for the field cannot be obtained
     * @throws UnsupportedTemporalTypeException if the field is not supported
     */
    @Override
    public ValueRange range(TemporalField field) {
        if (field instanceof ChronoField) {
            if (field == INSTANT_SECONDS || field == OFFSET_SECONDS) {
                return field.range();
            }
            return dateTime.range(field);
        }
        return field.rangeRefinedBy(this);
    }

    /**
     * Gets the value of the specified field from this date-time as an {@code int}.
     * <p>
     * This queries this date-time for the value of the specified field.
     * The returned value will always be within the valid range of values for the field.
     * If it is not possible to return the value, because the field is not supported
     * or for some other reason, an exception is thrown.
     * <p>
     * If the field is a {@link ChronoField} then the query is implemented here.
     * The {@link #isSupported(TemporalField) supported fields} will return valid
     * values based on this date-time, except {@code NANO_OF_DAY}, {@code MICRO_OF_DAY},
     * {@code EPOCH_DAY}, {@code PROLEPTIC_MONTH} and {@code INSTANT_SECONDS} which are too
     * large to fit in an {@code int} and throw an {@code UnsupportedTemporalTypeException}.
     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
     * <p>
     * If the field is not a {@code ChronoField}, then the result of this method
     * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
     * passing {@code this} as the argument. Whether the value can be obtained,
     * and what the value represents, is determined by the field.
     *
     * @param field  the field to get, not null
     * @return the value for the field
     * @throws DateTimeException if a value for the field cannot be obtained or
     *         the value is outside the range of valid values for the field
     * @throws UnsupportedTemporalTypeException if the field is not supported or
     *         the range of values exceeds an {@code int}
     * @throws ArithmeticException if numeric overflow occurs
     */
    @Override  // override for Javadoc and performance
    public int get(TemporalField field) {
        if (field instanceof ChronoField chronoField) {
            return switch (chronoField) {
                case INSTANT_SECONDS -> throw new UnsupportedTemporalTypeException("Invalid field " +
                                         "'InstantSeconds' for get() method, use getLong() instead");
                case OFFSET_SECONDS -> getOffset().getTotalSeconds();
                default -> dateTime.get(field);
            };
        }
        return ChronoZonedDateTime.super.get(field);
    }

    /**
     * Gets the value of the specified field from this date-time as a {@code long}.
     * <p>
     * This queries this date-time for the value of the specified field.
     * If it is not possible to return the value, because the field is not supported
     * or for some other reason, an exception is thrown.
     * <p>
     * If the field is a {@link ChronoField} then the query is implemented here.
     * The {@link #isSupported(TemporalField) supported fields} will return valid
     * values based on this date-time.
     * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
     * <p>
     * If the field is not a {@code ChronoField}, then the result of this method
     * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
     * passing {@code this} as the argument. Whether the value can be obtained,
     * and what the value represents, is determined by the field.
     *
     * @param field  the field to get, not null
     * @return the value for the field
     * @throws DateTimeException if a value for the field cannot be obtained
     * @throws UnsupportedTemporalTypeException if the field is not supported
     * @throws ArithmeticException if numeric overflow occurs
     */
    @Override
    public long getLong(TemporalField field) {
        if (field instanceof ChronoField chronoField) {
            return switch (chronoField) {
                case INSTANT_SECONDS -> toEpochSecond();
                case OFFSET_SECONDS -> getOffset().getTotalSeconds();
                default -> dateTime.getLong(field);
            };
        }
        return field.getFrom(this);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the zone offset, such as '+01:00'.
     * <p>
     * This is the offset of the local date-time from UTC/Greenwich.
     *
     * @return the zone offset, not null
     */
    @Override
    public ZoneOffset getOffset() {
        return offset;
    }

    /**
     * Returns a copy of this date-time changing the zone offset to the
     * earlier of the two valid offsets at a local time-line overlap.
     * <p>
     * This method only has any effect when the local time-line overlaps, such as
     * at an autumn daylight savings cutover. In this scenario, there are two
     * valid offsets for the local date-time. Calling this method will return
     * a zoned date-time with the earlier of the two selected.
     * <p>
     * If this method is called when it is not an overlap, {@code this}
     * is returned.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @return a {@code ZonedDateTime} based on this date-time with the earlier offset, not null
     */
    @Override
    public ZonedDateTime withEarlierOffsetAtOverlap() {
        ZoneOffsetTransition trans = getZone().getRules().getTransition(dateTime);
        if (trans != null && trans.isOverlap()) {
            ZoneOffset earlierOffset = trans.getOffsetBefore();
            if (earlierOffset.equals(offset) == false) {
                return new ZonedDateTime(dateTime, earlierOffset, zone);
            }
        }
        return this;
    }

    /**
     * Returns a copy of this date-time changing the zone offset to the
     * later of the two valid offsets at a local time-line overlap.
     * <p>
     * This method only has any effect when the local time-line overlaps, such as
     * at an autumn daylight savings cutover. In this scenario, there are two
     * valid offsets for the local date-time. Calling this method will return
     * a zoned date-time with the later of the two selected.
     * <p>
     * If this method is called when it is not an overlap, {@code this}
     * is returned.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @return a {@code ZonedDateTime} based on this date-time with the later offset, not null
     */
    @Override
    public ZonedDateTime withLaterOffsetAtOverlap() {
        ZoneOffsetTransition trans = getZone().getRules().getTransition(toLocalDateTime());
        if (trans != null) {
            ZoneOffset laterOffset = trans.getOffsetAfter();
            if (laterOffset.equals(offset) == false) {
                return new ZonedDateTime(dateTime, laterOffset, zone);
            }
        }
        return this;
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the time-zone, such as 'Europe/Paris'.
     * <p>
     * This returns the zone ID. This identifies the time-zone {@link ZoneRules rules}
     * that determine when and how the offset from UTC/Greenwich changes.
     * <p>
     * The zone ID may be same as the {@linkplain #getOffset() offset}.
     * If this is true, then any future calculations, such as addition or subtraction,
     * have no complex edge cases due to time-zone rules.
     * See also {@link #withFixedOffsetZone()}.
     *
     * @return the time-zone, not null
     */
    @Override
    public ZoneId getZone() {
        return zone;
    }

    /**
     * Returns a copy of this date-time with a different time-zone,
     * retaining the local date-time if possible.
     * <p>
     * This method changes the time-zone and retains the local date-time.
     * The local date-time is only changed if it is invalid for the new zone,
     * determined using the same approach as
     * {@link #ofLocal(LocalDateTime, ZoneId, ZoneOffset)}.
     * <p>
     * To change the zone and adjust the local date-time,
     * use {@link #withZoneSameInstant(ZoneId)}.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param zone  the time-zone to change to, not null
     * @return a {@code ZonedDateTime} based on this date-time with the requested zone, not null
     */
    @Override
    public ZonedDateTime withZoneSameLocal(ZoneId zone) {
        Objects.requireNonNull(zone, "zone");
        return this.zone.equals(zone) ? this : ofLocal(dateTime, zone, offset);
    }

    /**
     * Returns a copy of this date-time with a different time-zone,
     * retaining the instant.
     * <p>
     * This method changes the time-zone and retains the instant.
     * This normally results in a change to the local date-time.
     * <p>
     * This method is based on retaining the same instant, thus gaps and overlaps
     * in the local time-line have no effect on the result.
     * <p>
     * To change the offset while keeping the local time,
     * use {@link #withZoneSameLocal(ZoneId)}.
     *
     * @param zone  the time-zone to change to, not null
     * @return a {@code ZonedDateTime} based on this date-time with the requested zone, not null
     * @throws DateTimeException if the result exceeds the supported date range
     */
    @Override
    public ZonedDateTime withZoneSameInstant(ZoneId zone) {
        Objects.requireNonNull(zone, "zone");
        return this.zone.equals(zone) ? this :
            create(dateTime.toEpochSecond(offset), dateTime.getNano(), zone);
    }

    /**
     * Returns a copy of this date-time with the zone ID set to the offset.