Java Programs›Date & Time›Find the Day of the Week for a Date

Find the Day of the Week for a Date in Java

beginner· Date & Time · Date & Time

Problem

Every calendar date falls on one of seven weekdays; java.time represents them with the DayOfWeek enum, numbered from Monday (1) to Sunday (7).

Print the day of the week for three dates: 11 October 2026, 1 January 2000 and 20 July 1969.

Input

2000-01-01

Output

Saturday

Java Program

Java

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.format.TextStyle;
import java.util.Locale;

public class DayOfWeekForDate {
    public static void main(String[] args) {
        LocalDate[] dates = {
                LocalDate.of(2026, 10, 11),
                LocalDate.of(2000, 1, 1),
                LocalDate.of(1969, 7, 20)};

        for (LocalDate d : dates) {
            DayOfWeek day = d.getDayOfWeek();
            System.out.println(d + " is a " + day.getDisplayName(TextStyle.FULL, Locale.ENGLISH)
                    + " (day " + day.getValue() + " of the week)"); // Monday = 1 ... Sunday = 7
        }
    }
}

▶ Run Code

Output

2026-10-11 is a Sunday (day 7 of the week)
2000-01-01 is a Saturday (day 6 of the week)
1969-07-20 is a Sunday (day 7 of the week)

Core Logic

getDayOfWeek() computes the weekday from the date, and getDisplayName turns the enum into readable text.

How It Works

1Each LocalDate is created with LocalDate.of.
2getDayOfWeek() returns a DayOfWeek constant such as SUNDAY.
3getDisplayName(TextStyle.FULL, Locale.ENGLISH) gives Sunday; TextStyle.SHORT would give Sun.
4getValue() gives the ISO number, from Monday = 1 to Sunday = 7.

20 July 1969, the date of the first Moon landing, was a Sunday.

💡

Key Point: ISO numbering starts the week on Monday; if you need Sunday-first numbering, use WeekFields.SUNDAY_START rather than adjusting the numbers by hand.

Key Concepts

getDayOfWeek()DayOfWeekgetDisplayName()TextStyle

Approach 2: Zeller's Congruence (No Library)

Java

public class DayOfWeekZeller {
    public static void main(String[] args) {
        System.out.println("2026-10-11 is a " + dayName(2026, 10, 11));
        System.out.println("2000-01-01 is a " + dayName(2000, 1, 1));
    }

    // Zeller's congruence for the Gregorian calendar
    static String dayName(int year, int month, int day) {
        if (month < 3) { // January and February count as months 13 and 14 of the previous year
            month += 12;
            year -= 1;
        }
        int k = year % 100; // year within the century
        int j = year / 100; // the century
        int h = (day + 13 * (month + 1) / 5 + k + k / 4 + j / 4 + 5 * j) % 7;
        String[] names = {"Saturday", "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday"};
        return names[h]; // h = 0 is Saturday in Zeller's numbering
    }
}

▶ Run Code

Output

2026-10-11 is a Sunday
2000-01-01 is a Saturday

Core Logic

Zeller's congruence computes the weekday with pure arithmetic — a popular interview exercise that shows how calendar maths works.

How It Works

1January and February are treated as months 13 and 14 of the previous year, which moves the leap day to the end of the year.
2k is the year within the century and j is the century.
3The formula combines day, month, k, k/4, j/4 and 5j, then takes the result modulo 7.
4Zeller numbers the result from 0 = Saturday, so a lookup array maps it to a name.