Question

What day of the week is a given date? i.e. On what day of the week was 5 August 1967? if it is given that 1 January 1900 was a tuesday

Write a function is leap() which takes 1 input argument, an integer representing a year, and returns True if the year was a leap year, and False if it was not.

.Then, write a function days_since() which takes 3 input integers day, month, year, representing a date (after 1st January 1900), and returns the total number of days passed since the 1st January 1900. (For example, days_since(2, 1, 1900) should return 1.

Finally, write a function week_day() which takes 3 input integers day, month, year, representing a date (after 1st January 1900), and prints the day of the week corresponding to the date

Dont use any inbuilt function, use looping.

Answer 1

Function to check Leap year

static boolean isLeap(int year)
        {
                if (year % 400 == 0)
                        return true;
                if (year % 100 == 0)
                        return false;
                if (year % 4 == 0)
                        return true;
                return false;
        }

Function to return the total number of days passed since the 1st January 1900

static int monthDays[] = {31, 28, 31, 30, 31, 30, 
                                                        31, 31, 30, 31, 30, 31}; 
        static int countLeapYears(int m,int y) 
        { 
                int years = y; 
                if (m<= 2) 
                { 
                        years--; 
                } 
                return years / 4 - years / 100 + years / 400; 
        } 
        static int days_since(int d,int m,int y) 
        { 
                int n1 = 1900 * 365 + 1; 
                for (int i = 0; i < 1 - 1; i++) 
                { 
                        n1 += monthDays[i]; 
                } 
                n1 += countLeapYears(1,1900); 
                int n2 = y * 365 + d; 
                for (int i = 0; i < m - 1; i++) 
                { 
                        n2 += monthDays[i]; 
                } 
                n2 += countLeapYears(m,y); 
                return (n2 - n1); 
        } 

Function to prints the day of the week corresponding to the date

static String week_day(int d, int m, int y) 
{ 
    int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 }; 
    String d1[] = {"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
    y -= (m < 3) ? 1 : 0; 
    return d1[( y + y/4 - y/100 + y/400 + t[m-1] + d) % 7]; 
} 

All the above funcrions are putted in switch case to test

Source Code

import java.util.*;
public class Date
{
    static boolean isLeap(int year)
    {
        if (year % 400 == 0)
            return true;
        if (year % 100 == 0)
            return false;
        if (year % 4 == 0)
            return true;
        return false;
    }
    static int monthDays[] = {31, 28, 31, 30, 31, 30, 
                            31, 31, 30, 31, 30, 31}; 
    static int countLeapYears(int m,int y) 
    { 
        int years = y; 
        if (m<= 2) 
        { 
            years--; 
        } 
        return years / 4 - years / 100 + years / 400; 
    } 
    static int days_since(int d,int m,int y) 
    { 
        int n1 = 1900 * 365 + 1; 
        for (int i = 0; i < 1 - 1; i++) 
        { 
            n1 += monthDays[i]; 
        } 
        n1 += countLeapYears(1,1900); 
        int n2 = y * 365 + d; 
        for (int i = 0; i < m - 1; i++) 
        { 
            n2 += monthDays[i]; 
        } 
        n2 += countLeapYears(m,y); 
        return (n2 - n1); 
    } 
    static String week_day(int d, int m, int y) 
    { 
        int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 }; 
        String d1[] = {"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
        y -= (m < 3) ? 1 : 0; 
        return d1[( y + y/4 - y/100 + y/400 + t[m-1] + d) % 7]; 
    } 
    public static void main() 
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter 1 to check Leap Year\nEnter 2 to find the total number of days passed since the 1st January 1900\nEnter 3 to to prints the day of the week corresponding to the date");
        System.out.println("Enter your choice");
        int ch=sc.nextInt();
        switch(ch)
        {
            case 1: System.out.println("Enter year to check");
                    int year=sc.nextInt();
                    System.out.println(isLeap(year));break;
            case 2: System.out.println("Enter day to check");
                    int d=sc.nextInt();
                    System.out.println("Enter month to check");
                    int m=sc.nextInt();
                    System.out.println("Enter year to check");
                    int y=sc.nextInt();
                    System.out.println("Number of day since 1st january 1990 ="+days_since(d,m,y));break;
            case 3: System.out.println("Enter day to check");
                    int d1=sc.nextInt();
                    System.out.println("Enter month to check");
                    int m1=sc.nextInt();
                    System.out.println("Enter year to check");
                    int y1=sc.nextInt();
                    System.out.println("Day of the week is "+week_day(d1,m1,y1));break;
            default:System.out.println("Wrong Input");break;
           
        }
    }
}

Output of all Functions used above

Enter 1 to check Leap Year
Enter 2 to find the total number of days passed since the 1st January 1900
Enter 3 to to prints the day of the week corresponding to the date
Enter your choice
1
Enter year to check
2020
true
Enter 1 to check Leap Year
Enter 2 to find the total number of days passed since the 1st January 1900
Enter 3 to to prints the day of the week corresponding to the date
Enter your choice
2
Enter day to check
2
Enter month to check
1
Enter year to check
1990
Number of day since 1st january 1990 =32873
Enter 1 to check Leap Year
Enter 2 to find the total number of days passed since the 1st January 1900
Enter 3 to to prints the day of the week corresponding to the date
Enter your choice

2
Enter day to check
2
Enter month to check
1
Enter year to check
1900
Number of day since 1st january 1990 =1
Enter 1 to check Leap Year
Enter 2 to find the total number of days passed since the 1st January 1900
Enter 3 to to prints the day of the week corresponding to the date
Enter your choice
3
Enter day to check
13
Enter month to check
10
Enter year to check
2020
Day of the week isTuesday
Enter 1 to check Leap Year
Enter 2 to find the total number of days passed since the 1st January 1900
Enter 3 to to prints the day of the week corresponding to the date
Enter your choice
3
Enter day to check
13
Enter month to check
10
Enter year to check
2020
Day of the week is Tuesday