How to calculate if the difference between two dates is greater than 20 years?

Question

I have integers representing the month, day and year of two dates. How do I calculate if the difference between them is greater than 20 years? I used this on registration of new users.

Essentially a duplicate of http://stackoverflow.com/questions/3838527/android-java-date-difference-in-days ... — mikebabcock, Feb 07 '12 at 14:43
Wouldn't it really just be a comparison between if (year1+20) >= year2...? — Bry6n, Feb 07 '12 at 14:45
Its worth nothing that there is 365.25 days on average in a year (since 1901) Over a longer period of time its 365.2425 — Peter Lawrey, Feb 07 '12 at 15:54

Marsellus Wallace · Accepted Answer · 2012-02-08T05:09:18.147

Use Joda-Time, period! :)

Although "greater than 20 years" might be somewhat dependent on which kind of Calendar you're talking about, when you start counting, leap years, or daylight savings, Joda-Time will give you more flexibility that the util.Calendar class. Working with util.Date is not recommended and counting millisecond (or other things like that) will probably lead to buggy code.

JODA-TIME Code Samples:

Given:

int year1 = 2012, month1 = 2, day1 = 7;
int year2 = 1987, month2 = 7, day2 = 23;
//You can include a TimeZone if needed in the constructors below
DateTime dateTime1 = new DateTime(year1, month1, day1, 0, 0); //2012-02-07T00:00:00.000-05:00
DateTime dateTime2 = new DateTime(year2, month2, day2, 0, 0); //1987-07-23T00:00:00.000-04:00

Option 1, boring...

DateTime twentyYearsBefore = dateTime1.minusYears(20); //1992-02-07T00:00:00.000-05:00
if(dateTime2.compareTo(twentyYearsBefore) == -1)
    System.out.println("The difference between the dates is greater than 20 years");

Option 2, good stuff!

Days d = Days.daysBetween(dateTime1, dateTime2);
int days = d.getDays(); //-8965 days
System.out.println("There are " + days + " days between the two dates");

Option 3, rocket science!!! ;)

Period periodDifference = new Period(dateTime1, dateTime2);
System.out.println(periodDifference); //prints: P-24Y-6M-2W-1D

Of course the Period class has a ton of methods to get only the relevant fields. Click the following for the APIs of DateTime and Days

Thanks for the link to Joda, I hadn't run across that before, seems like a very useful date / time implementation. — FoamyGuy, Feb 09 '12 at 14:39

score 2 · Answer 2 · answered Feb 07 '12 at 14:44

Calendar Day1 = Calendar.getInstance();
Day1.set(Calendar.DAY_OF_MONTH, day1 - 1);
Day1.set(Calendar.MONTH, month1 - 1); // 0-11 so 1 less
Day1.set(Calendar.YEAR, year1);

Calendar Day2 = Calendar.getInstance();
Day2.set(Calendar.DAY_OF_MONTH, day2 - 1);
Day2.set(Calendar.MONTH, month2 - 1); // 0-11 so 1 less
Day2.set(Calendar.YEAR, year2);

long twenty_years = 31536000000 * 20;
long diff;
if(Day1.compareTo(Day2) == 1)
    long diff = Day1.getTimeInMillis() - Day2.getTimeInMillis();
else
    long diff = Day2.getTimeInMillis() - Day1.getTimeInMillis();

if(diff > twenty_years){
    // do something
}

score 2 · Answer 3 · answered Feb 07 '12 at 14:51

2

I think something simple as should do the trick.

double date1 = year + (month / 12.0) + (day / 365.0);
double date2 = year2 + (month2 / 12.0) + (day2 / 365.0);

if(Math.abs(date1 - date2) >= 20.0)

    //bigger

answered Feb 07 '12 at 14:51

warbio

466
5
16

Not sure if it could give wrong outputs becuase of leap years. – warbio Feb 07 '12 at 14:53

Joachim Isaksson · Answer 4 · 2012-02-07T14:55:58.553

1

This is a pretty simple way of doing it;

int date1 = year1 * 10000 + month1 * 100 + day1;
int date2 = year2 * 10000 + month2 * 100 + day2;
boolean greaterThan20 = (date2 - date1) >= 200000;

edited Feb 07 '12 at 14:55

answered Feb 07 '12 at 14:46

Joachim Isaksson

176,943
25
281
294

score 1 · Answer 5 · answered Feb 07 '12 at 14:47

1

the Calendar object would allow you to compare dates that way.

If you instantiate two Calendar objects one with each of your dates. Then roll one of them forward / backward by 20 years.

Once that is done either the .after(), or .before() methods will tell you what you need.

answered Feb 07 '12 at 14:47

FoamyGuy

46,603
18
125
156

if you roll by the year you might change smaller fields and I'm not sure if this would give the right answer in all the cases. It might depend on Damir's 20 years definition... – Marsellus Wallace Feb 07 '12 at 17:13
Good point, my method may end up being off by some hours / days depending on any calendar weirdness due to leap year or something else. – FoamyGuy Feb 07 '12 at 17:29

score 1 · Answer 6 · answered Feb 07 '12 at 14:51

1

You can use

Date(int year, int month, int date)

to get your values into a date format.

Then you can subtract one from the other and convert the value into years.

    java.util.Date lateDate, earlyDate;
    lateDate = Date(year1,month1,day1);
    earlyDate = Date(year2,month2,day2);
    deltaDays = ( lastDate.getTime() - earlyDate.getTime() )/ MILLSECS_PER_DAY;
    deltaDays = deltaDays / DAYS_IN_A_YEAR;

answered Feb 07 '12 at 14:51

Jpepper

437
3
15

Fine if you don't need to worry about leap years. – Peter Lawrey Feb 07 '12 at 15:53
Date(int year, int month, int date) is deprecated – Marsellus Wallace Feb 07 '12 at 17:01

How to calculate if the difference between two dates is greater than 20 years?

6 Answers6