Java Date and Time (java.time)

The modern date and time API is in the package java.time (Java 8+). Its objects are immutable and easy to use. Do not use the old java.util.Date and Calendar in new code.

The main classes

Class	Keeps
LocalDate	A date, with no time: 2026-03-15
LocalTime	A time, with no date: 14:30:00
LocalDateTime	Date and time, no time zone
ZonedDateTime	Date, time and time zone
Instant	A moment on the time line (UTC)
Period	An amount of time in years, months, days
Duration	An amount of time in hours, minutes, seconds

Create dates

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;

public class Main {
    public static void main(String[] args) {
        LocalDate date = LocalDate.of(2026, 3, 15);
        LocalTime time = LocalTime.of(14, 30);
        LocalDateTime both = LocalDateTime.of(date, time);

        System.out.println(date);
        System.out.println(time);
        System.out.println(both);
        System.out.println(date.getDayOfWeek());
        System.out.println(date.getMonth() + " " + date.getYear() + " " + date.getDayOfYear());
        System.out.println(date.isLeapYear());
        System.out.println(LocalDate.now().isAfter(date));     // now() is the real today
    }
}

Change and compare dates

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

public class DateMath {
    public static void main(String[] args) {
        LocalDate d = LocalDate.of(2026, 1, 31);
        System.out.println(d.plusDays(10));
        System.out.println(d.plusMonths(1));              // Feb has no 31st: goes to the last day
        System.out.println(d.minusYears(1));
        System.out.println(d.withDayOfMonth(1));
        System.out.println(d.isBefore(LocalDate.of(2026, 2, 1)));

        LocalDate start = LocalDate.of(2026, 1, 1);
        LocalDate end = LocalDate.of(2026, 12, 25);
        System.out.println(ChronoUnit.DAYS.between(start, end));
    }
}

Period and Duration

import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalTime;
import java.time.Period;

public class Span {
    public static void main(String[] args) {
        Period p = Period.between(LocalDate.of(2000, 5, 20), LocalDate.of(2026, 3, 15));
        System.out.println(p.getYears() + " years, " + p.getMonths() + " months, " + p.getDays() + " days");

        Duration d = Duration.between(LocalTime.of(9, 15), LocalTime.of(17, 45));
        System.out.println(d);
        System.out.println(d.toHours() + " h " + d.toMinutesPart() + " min");
    }
}

Format and parse

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class Fmt {
    public static void main(String[] args) {
        LocalDateTime dt = LocalDateTime.of(2026, 3, 5, 9, 7, 30);
        DateTimeFormatter f = DateTimeFormatter.ofPattern("dd/MM/yyyy HH:mm:ss");
        System.out.println(dt.format(f));
        System.out.println(dt.format(DateTimeFormatter.ofPattern("EEEE, d MMMM yyyy", java.util.Locale.ENGLISH)));
        System.out.println(dt.format(DateTimeFormatter.ISO_LOCAL_DATE));

        LocalDate parsed = LocalDate.parse("15-08-2026", DateTimeFormatter.ofPattern("dd-MM-yyyy"));
        System.out.println(parsed);
        System.out.println(LocalDate.parse("2026-08-15").plusDays(1));
    }
}

Letter	Meaning
yyyy	Year (4 digits)
MM	Month number (01 to 12)
MMM, MMMM	Month name (short, long)
dd	Day of month
HH	Hour (00 to 23)
mm	Minute
ss	Second
EEEE	Day name

Time zones

import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.LocalDateTime;

public class Zone {
    public static void main(String[] args) {
        LocalDateTime local = LocalDateTime.of(2026, 3, 15, 12, 0);
        ZonedDateTime india = local.atZone(ZoneId.of("Asia/Kolkata"));
        ZonedDateTime london = india.withZoneSameInstant(ZoneId.of("Europe/London"));
        ZonedDateTime newYork = india.withZoneSameInstant(ZoneId.of("America/New_York"));
        System.out.println(india);
        System.out.println(london);
        System.out.println(newYork);
    }
}

A wrong date

import java.time.LocalDate;

public class Bad {
    public static void main(String[] args) {
        LocalDate d = LocalDate.of(2026, 2, 30);
    }
}

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