Number of weeks between dates

Question

I have two Date values. I need to find number of weeks between them. I want to do it Apex Class. Not looking for formula fields.

So far I tried:

Integer numberofweeks = (projectStartDate - opp.Project_Start_Date__c)/7; 

I receive this error:

Date arithmetic expressions must use Integer or Long arguments

Answer 1

You need the Date.daysBetween method to get the difference between two Date values. The following works for me:

Date today = Date.today();
Date nextWeek = Date.today().addDays(7);
system.assertEquals(1, today.daysBetween(nextWeek)/7);

Answer 2

Here it is an example:

ApexTest:

@isTest
private class DateExampleTest {

    @isTest static void test_method_one() {
        //test 7 days diff
        Date startDate = Date.today().addDays(0);
        Date endDate = Date.today().addDays(7);

        Integer diffDays = startDate.daysBetween(endDate);

        System.debug(diffDays);
        System.assertEquals(7, diffDays);

        Integer diffWeeks = diffDays / 7;

        System.debug(diffWeeks);
        System.assertEquals(1, diffWeeks);

        //test 15 days diff
        startDate = Date.today().addDays(0);
        endDate = Date.today().addDays(15);

        diffDays = startDate.daysBetween(endDate);

        System.debug(diffDays);
        System.assertEquals(15, diffDays);

        diffWeeks = diffDays / 7;

        System.debug(diffWeeks);
        System.assertEquals(2, diffWeeks);

        //test 14 days diff back and forward
        startDate = Date.today().addDays(-7);
        endDate = Date.today().addDays(7);

        diffDays = startDate.daysBetween(endDate);

        System.debug(diffDays);
        System.assertEquals(14, diffDays);

        diffWeeks = diffDays / 7;

        System.debug(diffWeeks);
        System.assertEquals(2, diffWeeks);

    }

}

Answer 3

My initial approach would be to create a new formula field called "Number of Weeks " which would have the value of (date2-date1)/7

In the apex class you'd have something like

Integer x = date1.daysBetween(date2) /7;