Im trying to calculate the number off days between 2 date objects

Question

public static int countWeeks() {
    // setting dates
    Calendar calStart = GregorianCalendar.getInstance();
    calStart.set(2014, 8, 30);
    Date dateStart = calStart.getTime();

    Date dateEnd = new Date();

    // count days and weeks
    int diffInDays = Days.daysBetween(new DateTime(dateStart), new DateTime(dateEnd)).getDays(); //         int weekNumber = (int) diffInDays / 7;

    return weekNumber;

}

I'm trying to calculate the number of days and weeks between today and last week but I always get -3 as weekNumber. I have no idea what i'm doing wrong. Thanks in advance.

What is this `Days` class? If it is JodaTime, you should explain it since it is not part of Java API — SJuan76, Sep 07 '14 at 08:29
`int weekNumber` is commented out? So where is `weekNumber` declared? — Pang, Sep 07 '14 at 08:31
Also, remember that months in Calendar are 0-based, so you are actually setting the start at setember, 30th. Better use `Calendar.AUGUST` for that. — SJuan76, Sep 07 '14 at 08:33
Get the milliseconds, substract end from start. Divide by 1000 * 60 * 60 * 24. Have you day difference. — Hannes, Sep 07 '14 at 08:54

score 1 · Answer 1 · answered Sep 07 '14 at 08:36

1

First, I will assume that

int weekNumber = (int) diffInDays / 7;

is not commented since otherwise you would get a compilation error.

Now, as explained in my comment, by doing

calStart.set(2014, 8, 30);

You are setting the date at the end of setember, not of august. So, it is 3 weeks ahead of now, so you get a -3. Use the Calendar constants.

calStart.set(2014, Calendar.AUGUST, 30);

answered Sep 07 '14 at 08:36

SJuan76

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the weekNumber was indeed not suposed to be commented xd It works perfect now thanks :p – d4yl1ght Sep 07 '14 at 15:50

Rahul Tripathi · Answer 2 · 2014-09-07T08:40:31.093

0

You are getting -3 as the weeknumber since you have commented that out so it showing some random value. Also note that 8 shows the September month not Aug since months are 0 based.

So if you are aiming at August month then you may try this:

calStart.set(2014, 7, 30);
                   ^^-- This represents August month

edited Sep 07 '14 at 08:40

answered Sep 07 '14 at 08:32

Rahul Tripathi

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If the code was commented he would get a compilation error... – SJuan76 Sep 07 '14 at 08:33
@SJuan76:- Yes that makes sense. Then probably the issue is with the month as the gettime() will get the present date and the 8 is the September month as against the Aug which I guess OP is thinking :) – Rahul Tripathi Sep 07 '14 at 08:36

score 0 · Answer 3 · answered Sep 07 '14 at 08:39

You set the startdate to Sep. 30th because te month is zero bases!

See the documentation from java.util.Calendar:

public final void set(int year, int month, int date) Sets the values for the calendar fields YEAR, MONTH, and DAY_OF_MONTH. Previous values of other calendar fields are retained. If this is not desired, call clear() first. Parameters: year - the value used to set the YEAR calendar field. month - the value used to set the MONTH calendar field. Month value is 0-based. e.g., 0 for January. date - the value used to set the DAY_OF_MONTH calendar field. See Also:

score 0 · Answer 4 · answered Sep 07 '14 at 08:42

0

If you are on Java 8 you can use the Java time API:

LocalDate start = LocalDate.of(2014, 8, 30);
LocalDate end = LocalDate.now();
long days = ChronoUnit.DAYS.between(start, end);
return (int) days / 7;

answered Sep 07 '14 at 08:42

assylias

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Im trying to calculate the number off days between 2 date objects

4 Answers4