Working with Dates in Java: Overview of java.time, Joda-Time, and Apache Commons Libraries

Working with Dates in Java: Overview of Modern Libraries and Tools

Working with dates and times is one of the most common tasks in Java development. For a long time, the standard classes java.util.Date and java.util.Calendar were inconvenient, mutable, and error-prone. Fortunately, the situation has changed. In this overview, we will look at three main approaches: the built-in java.time package, the Joda-Time library, and Apache Commons Lang utilities.

1. java.time (Java 8+) — Modern Standard

Starting with Java 8, the java.time package, based on the ideas of Joda-Time, was included in the standard library. This is the primary and recommended way to work with dates in new projects.

Key classes:

• LocalDate — date without time (year, month, day).
• LocalTime — time without date (hours, minutes, seconds, nanoseconds).
• LocalDateTime — combination of date and time.
• ZonedDateTime — date and time with time zone.
• Instant — moment in time in UTC (machine-readable).
• Duration and Period — for working with time intervals.

Usage examples:

import java.time.*;import java.time.format.DateTimeFormatter;import java.time.temporal.ChronoUnit;

public class JavaTimeExample {    public static void main(String[] args) {        // Current date and time        LocalDate today = LocalDate.now();        LocalTime now = LocalTime.now();        System.out.println("Today: " + today);        System.out.println("Now: " + now);

        // Creating a specific date        LocalDate birthDate = LocalDate.of(1990, Month.MAY, 15);        System.out.println("Birth date: " + birthDate);

        // Working with time zones        ZonedDateTime berlinTime = ZonedDateTime.now(ZoneId.of("Europe/Berlin"));        ZonedDateTime tokyoTime = ZonedDateTime.now(ZoneId.of("Asia/Tokyo"));        System.out.println("In Berlin: " + berlinTime);        System.out.println("In Tokyo: " + tokyoTime);

        // Difference between dates        long daysBetween = ChronoUnit.DAYS.between(birthDate, today);        System.out.println("Days since birthday: " + daysBetween);

        // Formatting        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm");        String formatted = LocalDateTime.now().format(formatter);        System.out.println("Formatted: " + formatted);

        // Parsing a string        LocalDate parsedDate = LocalDate.parse("2023-12-31");        System.out.println("Parsed: " + parsedDate);    }}

2. Joda-Time — Time-Tested Alternative

Before the release of Java 8, Joda-Time was the de facto standard for working with dates. Currently, its use is justified only in legacy projects or when support for older Java versions (below 8) is needed.

Main features:

• Immutable objects — thread safety.
• Support for multiple calendar systems (Islamic, Buddhist, etc.).
• Simple and intuitive API.

Code example with Joda-Time:

import org.joda.time.*;import org.joda.time.format.DateTimeFormat;import org.joda.time.format.DateTimeFormatter;

public class JodaTimeExample {    public static void main(String[] args) {        // Current date and time        DateTime now = DateTime.now();        System.out.println("Now: " + now);

        // Creating a date        DateTime specificDate = new DateTime(2020, 6, 15, 10, 30, 0);        System.out.println("Specific date: " + specificDate);

        // Adding days        DateTime nextW