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Calendar.java
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public class Calendar {
public static boolean Leap(int n) {
if ((n % 4 == 0 && n % 100 != 0) || (n % 400 == 0))
return true;
return false;
}
public static int tempDate(int month, int year) {
if (month == 4 || month == 6 || month == 8 || month == 10 || month == 12)
return month;
else if (month == 1)
return Leap(year) ? 4 : 3;
else if (month == 3)
return 7;
else if (month == 9 || month == 5)
return month == 9 ? 5 : 9;
else if (month == 11 || month == 7)
return month == 7 ? 11 : 7;
return 0;
}
public static int yearOldDays(int year) {
int tensYear = year % 100;
year -= tensYear;
int sum = 0;
int yearOldays[] = { 5, 3, 1, 0 };
year = (year % 400) / 100;
// System.out.println(year);
if(year!=0)
sum += yearOldays[year - 1];
// System.out.println(sum);
int leapYearInTensYear = (int) tensYear / 4;
int nonleapYearInTensYear = tensYear - leapYearInTensYear;
// System.out.println(((leapYearInTensYear * 2) + nonleapYearInTensYear)%7);
sum += ((leapYearInTensYear * 2) + nonleapYearInTensYear) % 7;
// System.out.println(sum);
return sum;
}
public static int findFebLastDay(int year) {
int sum = Leap(year) ? 4 : 3;
// System.out.println(sum+yearOldDays(year-1));
return sum + yearOldDays(year-1);
}
public static void main(String[] args) {
String day[] = { "sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday" };
int date = 24, month = 04, year = 2002;
int febLastDay = findFebLastDay(year);
int tempDate = tempDate(month, year), tempDay = febLastDay;
if (tempDate == date)
System.out.println(day[tempDay]);
else {
int dayDifference = date - tempDate;
if(date>tempDate) {
tempDay = (tempDay+dayDifference) % 7;
} else {
tempDay = tempDay+dayDifference;
if(tempDay<0) {
tempDay+=7;
}
}
// System.out.println(tempDay);
System.out.println(day[tempDay]);
}
}
}
/*
Explaination:
0 - sunday
1 - monday
2 - tuesday
3 - wednesday
4 - thursday
5 - friday
7 - saturday
ODD DAYS:
No. of days cannot form a week is called odd days
To find odd days = ndays%7
365 days -> 52 weeks + 1 day (Here 1 day is a odd day)
366 days -> 52 weeks + 2 days (Here 2 days is a odd day)
years no.of odd days
100 - 5 days
200 - 3 days
300 - 1 days
400 - 0 days
Feb last day = (date/month) ==> 4/4, 6/6, 8/8,10/10,12/12,
9/5,5/9,11/7,7/11,
7/3
jan - 3(nonleap) and 4(leap)
eg: if feb 28 - friday
april 4 - friday
june 6 - friday
Example: 15/08/1947
Step 1: find the refrence date
1947%4 - not leap year
28/02/1947 --- this is the refrence date
28%7 = 0 odd days
month 1 has 31 days(31%7) = 3 odd days
Step 2: Find the no. of odd days in Previous year
1946 -> (1900+46)
1900 - 400+400+400+400+300 (find odd day for the year which are splited)
0 + 0 + 0 + 0 + 1 = 1 odd day
46/4 = 11 leapYear
(46-11) = 35 non leap year
11 leap year has (11*2) = 22 odd days
35 non leap year has (35*1) = 35 odd days
---------------
= 57 odd days
---------------
57%7 = 1 odd day
Step 3: Add all the odd days
0 + 3 + 1 + 1 = 5 ------> friday
Hence the Refrence date 28/02/1947 - friday
08/08/1947 - friday
08+07(1 week) = 15
15/08/1947 - friday
*/