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ZonedDateTime is a date-time type used to model a specific date and time within a particular time zone. It pairs a LocalDate and a LocalTime with a ZoneId, and it relies on the zone's rules to determine the offset from Coordinated Universal Time (UTC) for that date and time. This makes ZonedDateTime suitable for representing moments in history and future timestamps in a region-aware manner.

Because time zones can shift with daylight saving time, the same instant may correspond to different local times in different zones, and certain local times can be non-existent or ambiguous during transitions. ZonedDateTime exposes the rules of the associated zone so that such cases can be detected and handled explicitly.

Conversions and arithmetic: ZonedDateTime can be converted to an Instant, which pins it to a single point on the UTC timeline. It can also be transformed to another zone, preserving either the instant or the local date-time, via methods that reflect different semantics. The class is immutable; operations such as plus, minus, or withZoneSameInstant return new instances.

Formatting and parsing follow ISO-8601 conventions, producing or consuming strings that include the local date and time along with the zone identifier. Related types include LocalDateTime (date and time without a zone) and OffsetDateTime (date-time with a fixed offset but without the full zone rules). ZonedDateTime is widely used for scheduling, logging, and calendar calculations across multiple time zones.