Mastering Java Date & Time: SimpleDateFormat, Current Date Retrieval, and Date Comparison

This tutorial covers the essentials of working with dates and times in Java, including:

• Displaying the current date and time
• Formatting and parsing dates with SimpleDateFormat
• Comparing two dates

A Java Date object represents the following components:

• The year (2 or 4 digits)
• The month (numeric, three‑letter abbreviation, or full name)
• The day of month
• The day of week (e.g., Sun, Mon, Tue)

Computers support many additional date‑related parameters, which we’ll discuss in later sections.

Display Current Date in Java

Java’s java.util.Date class provides a simple way to obtain the current system date and time. Below is a minimal example:

import java.util.Date;
class DateExample {
    public static void main(String[] args) {
        Date current = new Date();
        System.out.println(current.toString());
    }
}

Output:

Wed Nov 29 06:36:22 UTC 2017

The output uses the default toString() format. To present the date in a custom layout, you need to format it explicitly.

SimpleDateFormat: Parse and Format Dates

Java formats dates using pattern strings that map letters to specific date components. Below is a reference table:

Refer to this table whenever you need to construct a specific format string.

Using SimpleDateFormat

The SimpleDateFormat class lets you define a pattern to format or parse dates. For example:

• Desired format: 2012.10.23 20:20:45 PST → pattern yyyy.MM.dd HH:mm:ss zzz
• Desired format: 09:30:00 AM 23-May-2012 → pattern hh:mm:ss a dd-MMM-yyyy

Tip: Pay careful attention to capitalization—using M for months and m for minutes is essential.

import java.text.SimpleDateFormat;
import java.util.Date;
class TestDatesFormat {
    public static void main(String[] args) {
        Date now = new Date();
        System.out.println(now);
        String pattern = "hh:mm:ss a dd-MMM-yyyy";
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        System.out.println(sdf.format(now));
    }
}

Output:

Wed Nov 29 06:31:41 UTC 2017
06:31:41 AM 29-Nov-2017

Comparing Dates

The most reliable method for date comparison in Java is compareTo(), which returns a negative value if the first date is earlier, zero if equal, and a positive value if later.

import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;
class TestDatesCompare {
    public static void main(String[] args) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
        Date date1 = sdf.parse("20-08-1981");
        Date date2 = sdf.parse("12-10-2012");
        System.out.println("Date1 : " + sdf.format(date1));
        System.out.println("Date2 : " + sdf.format(date2));
        if (date1.compareTo(date2) > 0) {
            System.out.println("Date 1 occurs after Date 2");
        } else if (date1.compareTo(date2) < 0) {
            System.out.println("Date 1 occurs before Date 2");
        } else {
            System.out.println("Both dates are the same");
        }
    }
}

Output:

Date1 : 20-08-1981
Date2 : 12-10-2012
Date 1 occurs before Date 2