JavaHow-ToBeginner · 3 min read

How to Format Date in Java: Simple Guide with Examples

In Java, you can format dates using DateTimeFormatter for modern code or SimpleDateFormat for legacy code. Use a pattern string like "yyyy-MM-dd" to specify the date format you want.

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Syntax

To format dates in Java, you use a formatter with a pattern string that defines how the date should look. The modern way is with DateTimeFormatter and the legacy way is with SimpleDateFormat.

DateTimeFormatter: Use DateTimeFormatter.ofPattern("pattern") where pattern is your date format.
SimpleDateFormat: Create an instance with new SimpleDateFormat("pattern") and call format(date).

Common pattern symbols include:

yyyy - year
MM - month number
dd - day of month
HH - hour (24-hour)
mm - minutes
ss - seconds

java

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.text.SimpleDateFormat;
import java.util.Date;

// Modern way
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

// Legacy way
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

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Example

This example shows how to format the current date and time using both DateTimeFormatter and SimpleDateFormat. It prints the formatted date as a string.

java

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatExample {
    public static void main(String[] args) {
        // Modern approach
        LocalDateTime now = LocalDateTime.now();
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        String formattedDateTime = now.format(formatter);
        System.out.println("Formatted date and time (modern): " + formattedDateTime);

        // Legacy approach
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String formattedDate = sdf.format(date);
        System.out.println("Formatted date and time (legacy): " + formattedDate);
    }
}

Output

Formatted date and time (modern): 2024-06-15 14:30:45 Formatted date and time (legacy): 2024-06-15 14:30:45

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Common Pitfalls

Common mistakes when formatting dates in Java include:

Using SimpleDateFormat without considering thread safety (it is not thread-safe).
Confusing pattern letters, for example, using mm for months instead of MM (where mm means minutes).
Not using the modern DateTimeFormatter which is thread-safe and recommended since Java 8.

java

import java.text.SimpleDateFormat;
import java.util.Date;

public class PitfallExample {
    public static void main(String[] args) {
        Date date = new Date();

        // Wrong pattern: 'mm' means minutes, not month
        SimpleDateFormat wrongFormat = new SimpleDateFormat("yyyy-mm-dd");
        System.out.println("Wrong format: " + wrongFormat.format(date));

        // Correct pattern: 'MM' means month
        SimpleDateFormat correctFormat = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println("Correct format: " + correctFormat.format(date));
    }
}

Output

Wrong format: 2024-30-15 Correct format: 2024-06-15

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Quick Reference

Pattern Symbol	Meaning	Example
yyyy	Year (4 digits)	2024
MM	Month (2 digits)	06
dd	Day of month (2 digits)	15
HH	Hour in 24h format (2 digits)	14
mm	Minutes (2 digits)	30
ss	Seconds (2 digits)	45

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Key Takeaways

Use DateTimeFormatter with a pattern string to format dates in modern Java.

SimpleDateFormat is legacy and not thread-safe; prefer DateTimeFormatter when possible.

Pattern letters are case-sensitive: 'MM' is month, 'mm' is minutes.

Always test your date format output to avoid confusion.

DateTimeFormatter is thread-safe and recommended since Java 8.