Java - Date & Time (java.time)

Date & Time (java.time)

Key Types

• LocalDate, LocalTime, LocalDateTime — no zone
• ZonedDateTime, OffsetDateTime — with zone/offset
• Instant — machine timestamp (UTC)
• Duration/Period — amount of time (time-based vs date-based)

Examples

import java.time.*;
LocalDate d = LocalDate.now();
LocalDateTime dt = LocalDateTime.now();
ZonedDateTime z = ZonedDateTime.now(ZoneId.of("UTC"));
Duration dur = Duration.between(Instant.now(), Instant.now().plusSeconds(5));
Period p = Period.between(LocalDate.of(2020,1,1), LocalDate.now());

Formatting and Parsing

import java.time.format.DateTimeFormatter;
String s = DateTimeFormatter.ISO_ZONED_DATE_TIME.format(z);
LocalDate parsed = LocalDate.parse("2024-10-15");

Time Zones

Always store in UTC (Instant) and convert to user-facing zones at the edges.

Try it

1. Parse a date string into LocalDate and format it in another style.
2. Convert a ZonedDateTime from your local zone to UTC and print both.