Here are simple and reliable ways to check whether a date falls on a weekend in Java. Prefer the modern java.time API (Java 8+), which is clearer and thread-safe.

• Using LocalDate (recommended)

import java.time.DayOfWeek;
import java.time.LocalDate;

public class WeekendChecker {
    public static boolean isWeekend(LocalDate date) {
        DayOfWeek dow = date.getDayOfWeek();
        return dow == DayOfWeek.SATURDAY || dow == DayOfWeek.SUNDAY;
    }

    public static void main(String[] args) {
        System.out.println(isWeekend(LocalDate.now())); // true or false
    }
}

• With time zones (e.g., when you start from an Instant)

import java.time.*;

public class WeekendCheckerTZ {
    public static boolean isWeekend(Instant instant, ZoneId zone) {
        DayOfWeek dow = instant.atZone(zone).getDayOfWeek();
        return dow == DayOfWeek.SATURDAY || dow == DayOfWeek.SUNDAY;
    }

    public static void main(String[] args) {
        boolean weekendInNY = isWeekend(Instant.now(), ZoneId.of("America/New_York"));
        System.out.println(weekendInNY);
    }
}

• If you still use the legacy Calendar API

import java.util.Calendar;

public class WeekendCheckerLegacy {
    public static boolean isWeekend(Calendar cal) {
        int dow = cal.get(Calendar.DAY_OF_WEEK);
        return dow == Calendar.SATURDAY || dow == Calendar.SUNDAY;
    }
}

• Configurable “weekend” definition (some regions consider Friday/Saturday)

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.util.EnumSet;
import java.util.Set;

public class ConfigurableWeekend {
    private static final Set<DayOfWeek> DEFAULT_WEEKEND = EnumSet.of(DayOfWeek.SATURDAY, DayOfWeek.SUNDAY);

    public static boolean isWeekend(LocalDate date, Set<DayOfWeek> weekendDays) {
        return weekendDays.contains(date.getDayOfWeek());
    }

    public static void main(String[] args) {
        System.out.println(isWeekend(LocalDate.now(), DEFAULT_WEEKEND));
        // Example for Fri/Sat weekend:
        Set<DayOfWeek> friSatWeekend = EnumSet.of(DayOfWeek.FRIDAY, DayOfWeek.SATURDAY);
        System.out.println(isWeekend(LocalDate.now(), friSatWeekend));
    }
}

Notes:

• Use java.time classes (LocalDate, ZonedDateTime, DayOfWeek) for new code.
• If you have a timestamp without a zone (Instant), convert with a ZoneId before checking the day of the week.