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Program to find differences of two dates in days in java

Here, we are implementing a java program that will read (have) two dates and print their differences in dates.
Submitted by IncludeHelp, on December 24, 2017

Given two days and we have to find their differences in number of days using java program.

In this program, we are reading dates from the user (using 'BufferedReader' class) and then validating the dated, if the dates are valid, program will find and print their differences in number of days.

Example:

    Input
    Enter the first date in (dd/mm/yyyy) format: 12/12/2016
    Enter the second date in (dd/mm/yyyy) format: 12/12/2017

    Output
    Days between 12/12/2016  and 12/12/2017  is : 365 days.

Program

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ExCalculateDays {
  // create buffer class object.
  static BufferedReader BR = new BufferedReader(new InputStreamReader(System.in));
  int month[] = {
    0,
    31,
    28,
    31,
    30,
    31,
    30,
    31,
    31,
    30,
    31,
    30,
    31
  };

  //create function for checking Leap Year or not. 
  int isLeap(int y) {
    if ((y % 400 == 0) || ((y % 100 != 0) && (y % 4 == 0)))
      return 29;
    else
      return 28;
  }

  // create function for checking date is valid or not.
  boolean dateValidate(int d, int m, int y) {
    month[2] = isLeap(y);
    if (m < 0 || m > 12 || d < 0 || d > month[m] || y < 0 || y > 9999)
      return false;
    else
      return true;
  }

  // this function calculate days between given dates. 
  int dayno(int d, int m, int y) {
    int dn = 0;
    month[2] = isLeap(y);
    for (int i = 1; i < m; i++) {
      dn = dn + month[i];
    }
    dn = dn + d;
    for (int i = 1; i < y; i++) {
      if (isLeap(i) == 29)
        dn = dn + 366;
      else
        dn = dn + 365;
    }
    return dn;
  }

  public static void main(String args[]) throws IOException {
    ExCalculateDays CD = new ExCalculateDays();

    // Enter the dates one by one.
    System.out.print("Enter the first date in (dd/mm/yyyy) format: ");
    String date1 = BR.readLine().trim();
    int p, q;

    // calculate the days.
    p = date1.indexOf("/");
    int d1 = Integer.parseInt(date1.substring(0, p));

    //calculating the month
    q = date1.lastIndexOf("/");
    int m1 = Integer.parseInt(date1.substring(p + 1, q));

    // calculating the year
    int y1 = Integer.parseInt(date1.substring(q + 1));

    System.out.print("Enter the second date in (dd/mm/yyyy) format: ");
    String date2 = BR.readLine().trim();

    p = date2.indexOf("/");
    int d2 = Integer.parseInt(date2.substring(0, p));

    q = date2.lastIndexOf("/");
    int m2 = Integer.parseInt(date2.substring(p + 1, q));
    int y2 = Integer.parseInt(date2.substring(q + 1));

    // check for valid input of dates.
    if (CD.dateValidate(d1, m1, y1) == true && CD.dateValidate(d2, m2, y2) == true) {
      int a = CD.dayno(d1, m1, y1);
      int b = CD.dayno(d2, m2, y2);

      // print the final result.
      System.out.print("Days between " + date1 + " " + " and " + date2 + " " + " is : " + Math.abs(a - b) + " days.");
    } else
      // otherwise invalid input of dates.
      System.out.println("Invalid Dates...");
  }
}

Output

First run:
Enter the first date in (dd/mm/yyyy) format: 12/12/2016
Enter the second date in (dd/mm/yyyy) format: 12/12/2017
Days between 12/12/2016  and 12/12/2017  is : 365 days.

Second run:
Enter the first date in (dd/mm/yyyy) format: 12/2017/12
Enter the second date in (dd/mm/yyyy) format: 22/2017/12
Invalid Dates...

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