LocalDate, LocalTime, LocalDateTime

Overview

The java.time package (introduced in Java 8) provides immutable, thread-safe date and time classes. The three core types that represent date and/or time without a time zone are:

None of these classes store timezone or offset information. Use ZonedDateTime or OffsetDateTime when timezone is needed.

LocalDate

Represents a date: year, month, and day-of-month.

Creating a LocalDate

java
LocalDate today    = LocalDate.now();              // current date from system clock
LocalDate birthday = LocalDate.of(1990, 3, 15);   // March 15, 1990
LocalDate holiday  = LocalDate.of(2025, Month.DECEMBER, 25);  // using Month enum
LocalDate parsed   = LocalDate.parse("2025-06-15"); // ISO format: yyyy-MM-dd

Reading Fields

java
LocalDate d = LocalDate.of(2025, 6, 15);
d.getYear();         // 2025
d.getMonthValue();   // 6
d.getMonth();        // Month.JUNE
d.getDayOfMonth();   // 15
d.getDayOfWeek();    // DayOfWeek.SUNDAY
d.getDayOfYear();    // 166
d.isLeapYear();      // false
d.lengthOfMonth();   // 30

Manipulating Dates (Immutable — always returns new object)

java
LocalDate d = LocalDate.of(2025, 6, 15);
d.plusDays(10);         // 2025-06-25
d.plusWeeks(1);         // 2025-06-22
d.plusMonths(2);        // 2025-08-15
d.plusYears(1);         // 2026-06-15
d.minusDays(5);         // 2025-06-10
d.withDayOfMonth(1);    // 2025-06-01
d.withMonth(1);         // 2025-01-15

Exam tip: Date-time classes are immutable. Calling d.plusDays(10) does not modify d — it returns a new LocalDate. You must assign the result.

Comparing Dates

java
LocalDate d1 = LocalDate.of(2025, 1, 1);
LocalDate d2 = LocalDate.of(2025, 6, 15);

d1.isBefore(d2);        // true
d1.isAfter(d2);         // false
d1.isEqual(d2);         // false
d1.compareTo(d2);       // negative (d1 is earlier)

LocalTime

Represents a time-of-day: hours, minutes, seconds, and nanoseconds.

Creating a LocalTime

java
LocalTime now     = LocalTime.now();
LocalTime morning = LocalTime.of(9, 30);           // 09:30:00
LocalTime precise = LocalTime.of(10, 15, 30, 500); // 10:15:30.000000500
LocalTime parsed  = LocalTime.parse("14:30:00");   // ISO format: HH:mm:ss

Constants:

java
LocalTime.MIN;       // 00:00:00
LocalTime.MAX;       // 23:59:59.999999999
LocalTime.MIDNIGHT;  // 00:00:00
LocalTime.NOON;      // 12:00:00

Reading Fields

java
LocalTime t = LocalTime.of(14, 30, 45, 100_000_000);
t.getHour();         // 14
t.getMinute();       // 30
t.getSecond();       // 45
t.getNano();         // 100000000

Manipulating Time

java
LocalTime t = LocalTime.of(10, 0);
t.plusHours(3);       // 13:00
t.plusMinutes(90);    // 11:30
t.minusSeconds(30);   // 09:59:30
t.withHour(8);        // 08:00

Times wrap around at midnight:

java
LocalTime.of(23, 0).plusHours(2);  // 01:00 (next day — no date stored)

LocalDateTime

Combines a LocalDate and a LocalTime into a single object, still without timezone.

Creating a LocalDateTime

java
LocalDateTime now  = LocalDateTime.now();
LocalDateTime dt   = LocalDateTime.of(2025, 6, 15, 10, 30);      // date + time
LocalDateTime dt2  = LocalDateTime.of(2025, Month.JUNE, 15, 10, 30, 0);
LocalDateTime dt3  = LocalDateTime.parse("2025-06-15T10:30:00"); // ISO 8601

// From existing LocalDate and LocalTime
LocalDate     date = LocalDate.of(2025, 6, 15);
LocalTime     time = LocalTime.of(10, 30);
LocalDateTime dt4  = LocalDateTime.of(date, time);
LocalDateTime dt5  = date.atTime(time);
LocalDateTime dt6  = date.atTime(10, 30);
LocalDateTime dt7  = time.atDate(date);

Extracting Parts

java
LocalDateTime dt = LocalDateTime.of(2025, 6, 15, 10, 30, 45);
dt.toLocalDate();    // LocalDate: 2025-06-15
dt.toLocalTime();    // LocalTime: 10:30:45
dt.getYear();        // 2025
dt.getHour();        // 10

Manipulating LocalDateTime

All manipulation methods work the same as LocalDate and LocalTime:

java
LocalDateTime dt = LocalDateTime.of(2025, 6, 15, 10, 30);
dt.plusDays(1);       // 2025-06-16T10:30
dt.plusHours(5);      // 2025-06-15T15:30
dt.minusWeeks(1);     // 2025-06-08T10:30
dt.withMonth(12);     // 2025-12-15T10:30

The Month and DayOfWeek Enums

java
// Month enum
Month.JANUARY.getValue();     // 1
Month.DECEMBER.getValue();    // 12
Month.JUNE.maxLength();       // 30
Month.FEBRUARY.maxLength();   // 29 (uses leap year for max)

// DayOfWeek enum
DayOfWeek.MONDAY.getValue();  // 1
DayOfWeek.SUNDAY.getValue();  // 7

Formatting and Parsing

java
import java.time.format.DateTimeFormatter;

DateTimeFormatter fmt = DateTimeFormatter.ofPattern("dd/MM/yyyy");
String formatted = LocalDate.of(2025, 6, 15).format(fmt);  // "15/06/2025"

LocalDate parsed = LocalDate.parse("15/06/2025", fmt);     // 2025-06-15

// Predefined formatters
LocalDate.now().format(DateTimeFormatter.ISO_LOCAL_DATE);   // "2025-06-15"

Key Points for the Exam

• LocalDate, LocalTime, and LocalDateTime are immutable — mutations return new instances.
• Month values in LocalDate.of() are 1-based (1 = January, 12 = December).
• The Month enum values are JANUARY through DECEMBER; getMonthValue() returns 1–12.
• LocalTime wraps around midnight — it has no concept of date overflow.
• parse() defaults to ISO 8601 format; use a DateTimeFormatter for other formats.
• Use .atTime() and .atDate() to combine LocalDate and LocalTime into LocalDateTime.

References

• Oracle Docs — LocalDate (Java SE 25)
• Oracle Docs — LocalTime (Java SE 25)
• Oracle Docs — LocalDateTime (Java SE 25)