Calculating days between two dates in JAVA (catch ParseException error)

Question

I’m trying to calculate the number of days between 2 dates. When I run this, it throws the catch (ParseException ex).

import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;
import java.util.concurrent.TimeUnit;

public class Main {

    public static void main(String[] args) {

        String date1 = "11/11/2020";
        String date2 = "13/11/2020";

        try {
            SimpleDateFormat dateFormat = new SimpleDateFormat("dd-mm-yyyy");
            Date date_1 = dateFormat.parse(date1);
            Date date_2 = dateFormat.parse(date2);

            System.out.println(date_1);
            System.out.println(date_2);

            long numberOfDays = date_2.getTime() - date_1.getTime();
            numberOfDays = TimeUnit.DAYS.convert(numberOfDays, TimeUnit.MILLISECONDS);

            System.out.println(numberOfDays);

        } 
        catch (ParseException ex)
        {
            System.out.println("error");
        }
    }
}

other than the catch, there are no errors, so I’m kind of lost.

"other than the catch, there are no errors, so I’m kind of lost."... well, should you maybe print what the exception says? — eis
– eis, Commented Mar 9, 2020 at 13:32
Change date strings to use '-' instead of '/' eg. "11-11-2020". Or change the SimpleDateFormat string to look like this: "dd/mm/yyyy" — mTv
– mTv, Commented Mar 9, 2020 at 13:33
Statement "it throws the catch (ParseException ex)" is really weird. By it's nature a "catch" block catches the exception, not throws it (well, you can rethrow something inside of it). It is recommended to properly handle the caught expection, eg. at least use e.printStackTrace(); instead of System.out.println("error"); — Amongalen
– Amongalen, Commented Mar 9, 2020 at 13:38
As I suggested in my answer, Date is quite deprecated and should not be used. LocalDate is the way to go for date related code. — WJS
– WJS, Commented Mar 9, 2020 at 14:27
I recommend you don’t use SimpleDateFormat and Date. Those classes are poorly designed and long outdated, the former in particular notoriously troublesome. Also converting milliseonds to days may give inaccurate results across summer time (DST) transistions and similar. Instead use LocalDate, DateTimeFormatter and ChronoUnit.DAYS.between(), all from java.time, the modern Java date and time API. — Anonymous
– Anonymous, Commented Mar 9, 2020 at 19:12

WJS · Accepted Answer · 2020-03-09 13:42:14Z

5

Don't use Date. Try this.

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        String date1 = "11/11/2020";
        String date2 = "13/11/2020";

        LocalDate d1 = LocalDate.parse(date1,dtf);
        LocalDate d2 = LocalDate.parse(date2,dtf);

        long ndays = d1.datesUntil(d2).count();
        System.out.println(ndays);

answered Mar 9, 2020 at 13:42

WJS

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Comments

jeprubio · Accepted Answer · 2020-03-09 14:11:08Z

4

If you had printed the catched exception:

System.out.println("error: " + ex.getLocalizedMessage());

You would have seen:

error: Unparseable date: "11/11/2020"

The problem is in:

SimpleDateFormat dateFormat = new SimpleDateFormat("dd-mm-yyyy");

change it to:

SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");

Since the provided dates are in that format.

edited Mar 9, 2020 at 14:11

answered Mar 9, 2020 at 13:33

jeprubio

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3 Comments

WJS Over a year ago

According to the JavaDoc, mm stands for minutes.

jeprubio Over a year ago

@WJS You are right, well spotted, it had more than one bug then. I update the answer, thanks

Anonymous Over a year ago

java.time would have made you aware of the incorrect case of mm. One more reason to use it instead of the troublesome SimpleDateFormat.

Filippos Georgiou · Accepted Answer · 2020-03-09 13:46:38Z

3

If Java 8 is an option I'd recommend using the Time API.

Example:

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;

public class Main
{
    public static void main(String[] args) {
        DateTimeFormatter format = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        String date1 = "11/11/2020";
        String date2 = "13/11/2020";

        LocalDate firstDate = LocalDate.parse(date1, format);
        LocalDate secondDate = LocalDate.parse(date2, format);

        long days = ChronoUnit.DAYS.between(firstDate, secondDate);
        System.out.println("Days between: " + days);
    }
}

answered Mar 9, 2020 at 13:46

Filippos Georgiou

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1 Comment

Filippos Georgiou Over a year ago

@WJS beat me to it :P

Thanos M · Accepted Answer · 2020-03-10 09:44:14Z

3

Just change this :

 SimpleDateFormat dateFormat = new SimpleDateFormat("dd-mm-yyyy");

to that :

SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");

The date you are trying to parse 11/11/2020 does not match the date format you are trying to use dd-mm-yyyy

You can resolve problems like that on your own by printing out the stack trace inside catch :

ex.printStackTrace();

edited Mar 10, 2020 at 9:44

answered Mar 9, 2020 at 13:33

Thanos M

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1 Comment

WJS Over a year ago

change mm to MM (minutes to Month).

Tayyab Razaq · Accepted Answer · 2020-03-09 20:21:24Z

2

First, you have different formats in input dates and defined format. Therefore, you're getting a parsing exception.

Secondly, We can java.time.Duration class in Java8 for such calculation. Example:

public static void main(String[] args) throws ParseException {
    String date1 = "11/11/2020";
    String date2 = "13/11/2020";
    DateFormat format = new SimpleDateFormat("dd/MM/yyyy");

    Duration duration = Duration.between(format.parse(date1).toInstant(), format.parse(date2).toInstant());
    System.out.println("Days between: " + duration.toDays());
}

edited Mar 9, 2020 at 20:21

answered Mar 9, 2020 at 18:38

Tayyab Razaq

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3 Comments

Anonymous Over a year ago

I agree that using java.time since Java 8 is a great improvement. Still better: (1) Drop the use of the old DateFormat, SimpleDateFormat and Date completely. (2) Use ChronoUnit.DAYS.between() rather than Duration. BTW lower case mm is incorrect for month.

Tayyab Razaq Over a year ago

Thanks @OleV.V 1 & 2 are good suggestions 3) mm is working fine with SimpleDateFormat but not work in DateTimeFormatter.

Tayyab Razaq Over a year ago

Oooh! My bad. I did not notice that. You're right. Thanks

Nahuel Giani · Accepted Answer · 2020-03-09 13:34:46Z

1

Your pattern is incorrect.

You use:

new SimpleDateFormat("dd-mm-yyyy");

but you need use:

new SimpleDateFormat("dd/mm/yyyy");

because yours date's have "/" instead of "-"

answered Mar 9, 2020 at 13:34

Nahuel Giani

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