102  * the local time.
 103  * <p>
 104  * For example, consider adding a period of one day and a duration of one day to
 105  * 18:00 on the evening before a daylight savings gap. The {@code Period} will add
 106  * the conceptual day and result in a {@code ZonedDateTime} at 18:00 the following day.
 107  * By contrast, the {@code Duration} will add exactly 24 hours, resulting in a
 108  * {@code ZonedDateTime} at 19:00 the following day (assuming a one hour DST gap).
 109  * <p>
 110  * The supported units of a period are {@link ChronoUnit#YEARS YEARS},
 111  * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
 112  * All three fields are always present, but may be set to zero.
 113  * <p>
 114  * The ISO-8601 calendar system is the modern civil calendar system used today
 115  * in most of the world. It is equivalent to the proleptic Gregorian calendar
 116  * system, in which today's rules for leap years are applied for all time.
 117  * <p>
 118  * The period is modeled as a directed amount of time, meaning that individual parts of the
 119  * period may be negative.
 120  *
 121  * <p>
 122  * This is a <a href="{@docRoot}/java/lang/doc-files/ValueBased.html">value-based</a>
 123  * class; use of identity-sensitive operations (including reference equality
 124  * ({@code ==}), identity hash code, or synchronization) on instances of
 125  * {@code Period} may have unpredictable results and should be avoided.
 126  * The {@code equals} method should be used for comparisons.
 127  *
 128  * @implSpec
 129  * This class is immutable and thread-safe.
 130  *
 131  * @since 1.8
 132  */
 133 public final class Period
 134         implements ChronoPeriod, Serializable {
 135 
 136     /**
 137      * A constant for a period of zero.
 138      */
 139     public static final Period ZERO = new Period(0, 0, 0);
 140     /**
 141      * Serialization version.
 142      */

 102  * the local time.
 103  * <p>
 104  * For example, consider adding a period of one day and a duration of one day to
 105  * 18:00 on the evening before a daylight savings gap. The {@code Period} will add
 106  * the conceptual day and result in a {@code ZonedDateTime} at 18:00 the following day.
 107  * By contrast, the {@code Duration} will add exactly 24 hours, resulting in a
 108  * {@code ZonedDateTime} at 19:00 the following day (assuming a one hour DST gap).
 109  * <p>
 110  * The supported units of a period are {@link ChronoUnit#YEARS YEARS},
 111  * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
 112  * All three fields are always present, but may be set to zero.
 113  * <p>
 114  * The ISO-8601 calendar system is the modern civil calendar system used today
 115  * in most of the world. It is equivalent to the proleptic Gregorian calendar
 116  * system, in which today's rules for leap years are applied for all time.
 117  * <p>
 118  * The period is modeled as a directed amount of time, meaning that individual parts of the
 119  * period may be negative.
 120  *
 121  * <p>
 122  * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 123  * class; use of identity-sensitive operations (including reference equality
 124  * ({@code ==}), identity hash code, or synchronization) on instances of
 125  * {@code Period} may have unpredictable results and should be avoided.
 126  * The {@code equals} method should be used for comparisons.
 127  *
 128  * @implSpec
 129  * This class is immutable and thread-safe.
 130  *
 131  * @since 1.8
 132  */
 133 public final class Period
 134         implements ChronoPeriod, Serializable {
 135 
 136     /**
 137      * A constant for a period of zero.
 138      */
 139     public static final Period ZERO = new Period(0, 0, 0);
 140     /**
 141      * Serialization version.
 142      */