How to get difference between two dates in years, months and days?

How do I calculate the number of days between two given dates? (Program provided)?

• I am stuck trying to figure this one out. Any help/hints/suggestions are more than appreciated. I typed the program out below all by myself and it's all that I have so far... It can compile and run, but I'm having difficulty trying to make it calculate the difference between two given dates. import java.util.Scanner; /** * Days determines the number of days between two dates. * @author Vince Luc */ public class Days { public static void main(String[] args) { String start = "02/23/2011"; // replace with input String end = "04/15/2011"; // replace with input System.out.printf("Days between %s and %s are %d.\n", start, end, daysBetweenDates(start, end)); Scanner kbd = new Scanner(System.in); Scanner input = new Scanner(System.in); int month; int day; int year; start = "02/23/2011"; end = "04/15/2011"; System.out.print("Please enter value of a year: "); year = input.nextInt(); if (isLeapYear(year)) System.out.println("The year " + year + " is a leap year."); else System.out.println("The year " + year + " is not a leap year."); } /** * isLeapYear determines whether a year is a leap year or not * @param year (int) Years since recognized beginning of C.E. * @return (boolean) true if year divisible by 4 (but not 100) */ public static boolean isLeapYear(int year) { boolean valueToReturn; if (year % 4 == 0 && year % 100 != 0) valueToReturn = true; else if (year % 400 == 0) valueToReturn = true; else valueToReturn = false; return valueToReturn; } /** * daysInMonth looks up the number of days in the specified month * @param month (int) a number between 1 and 12 indicating the desired month * @param year (int) the year is only meaningful for February (2) * @return (int) the last day of month/year (or 0 if invalid month provided) */ public static int daysInMonth(int month, int year) { int daysToReturn; System.out.println("calculating days of month " + month + "in year " + year); switch (month) { case 1: daysToReturn = 31; break; case 3: daysToReturn = 31; break; case 4: daysToReturn = 30; break; case 5: daysToReturn = 31; break; case 6: daysToReturn = 30; break; case 7: daysToReturn = 31; break; case 8: daysToReturn = 31; break; case 9: daysToReturn = 30; break; case 10: daysToReturn = 31; break; case 11: daysToReturn = 30; break; case 12: daysToReturn = 31; break; // finish code for cases 1, 3, 5, 7, 8, 10, and 12 case 2: if (isLeapYear(year)) daysToReturn = 29; else daysToReturn = 28; break; default: daysToReturn = 0; // It should not occur } return daysToReturn; } /** * daysIntoYear translates a date (month, day, year) into a single number * representing the days since 12/31/(year-1). * @param month (int) 1-12, where 1 is January and 12 is December * @param day (int) 1-31, or actually up to daysInMonth * @param year (int) years since start of C.E. * @return (int) number of days between 12/31/(year-1) and (month)/(day)/(year) */ public static int daysIntoYear(int month, int day, int year) { if ( isLeapYear(year) ) return 366; else return 365; } /** * daysBetweenDates calculates number of days between two dates. * @param start (String) starting date * @param end (String) ending date, presumably later than start * @return (int) days between start date and end date */ public static int daysBetweenDates(String start, String end) { int days = 0; System.out.println("calculating daysBetweenDates"); return days; } }

• Answer:

  This will make it VERY hard for you to find the exact amount of days between a date. You'd have to manually keep track of which months have 30 days and which months have 31 days. You'd have to keep track of leap-years manually. I don't recommend you to do this WHATSOEVER. What I do recommend you to do is using the calendar class, which I provided an example for: public static void main(String[] args) { //Make an instance of a calendar Calendar start = Calendar.getInstance(); //Set the time of the calendar. Remember though, in the calendar class, //you'll have to watch out with months. Because January would be 0, //February would be 1, March would be 2, etc. That's why I've set the //month to 01 instead of 02 like you did. start.set(2011, 01, 23); //Creating another instance of the calendar. This would be //your specified ending date Calendar end = Calendar.getInstance(); //Setting this ending date end.set(2011, 03, 15); //This is the calendar which we use to copy the starting calendar, because //contrary to the starting calendar, we need to alter this one so we clone start. Calendar dayCalculator = (Calendar) start.clone(); //The long in which we're gonna save the amount of days long amountOfDays = 0; //This part of the program checks if dayCalculator comes before end. If it does, it's going to //add 1 day to the dayCalculator, and 1 to the amountOfDays. It will keep adding 1 day to //our start clone, and 1 to our long amountOfDays until dayCalculator has reached end, and //they are now both equal dates. That ways you will have counted all the days from start //to end without using any kind of elaborate String techniques while (dayCalculator.before(end)) { dayCalculator.add(Calendar.DAY_OF_MO... 1); amountOfDays++; } //Here it will print the amount of days. You can alter this code to your liking. //I would suggest changing it into a separate method for convenience. System.out.println(amountOfDays); } Hope I helped. Good luck. EDIT: It's supposed to be Calendar.add(Calendar.DAY_OF_MONTH, 1) I don't know why Yahoo is changing the "MONTH" part into dots...