Add 5 Business days calculates wrong Target Date value in salesforce?

Question

Business hours is set to 7 AM to 7 PM Mon to Fri, Time Zone (GMT-05:00) Eastern Standard Time (America/New_York).

I need to simply add 5 working days from Current Date in order to calculate the target Date. I simply used BusinessHours.add API.

Long bMilliSec = 5*12*60*60*1000;
System.debug('LONG VALUE :: '+bMilliSec);
Date startDate = Date.today();
DateTime startDateTime = DateTime.newInstance(startDate.year(), startDate.month(), startDate.day());
BusinessHours bh = [SELECT Id,Name,IsActive,IsDefault,MondayEndTime,MondayStartTime 
                    FROM BusinessHours 
                    WHERE Name = 'ZZZZZZ'];
DateTime businessEndDateTime = BusinessHours.add(bh.Id,startDateTime,bMilliSec);
System.debug('########## :: '+businessEndDateTime);

The below 2 days are holidays:

• 2/14/2018 All Day
• 2/12/2018 All Day

Why would I get a result of 22-Feb-2018 instead of 21-Feb-2018?

Some testing around this..

I created an Adhoc Request (for estimated completion date) is 2 days which should be 2/14/2018 but instead it’s displaying 2/13/2018. I created a content request,(for estimated completion date) is 2 days is 5 days which should be 2/19/2018 but instead it’s displaying 2/21/2018.

Some Crazy Calculations are happening

• if I add 2 days = 2018-02-17 00:00:00
• if I add 3 days = 2018-02-20 00:00:00
• If I add 4 days = 2018-02-21 00:00:00
• If I add 5 days = 2018-02-22 00:00:00

Answer 1

As per salesforce docs: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_businesshours.htm, and https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_datetime.htm#apex_methods_system_datetime

I am formatting date which returns : Converts the date to the local time zone and returns the converted date as a formatted string using the locale of the context user. If the time zone cannot be determined, GMT is used..

global static Date getBusinessTargetDate(DateTime startDate, Integer businessDays){
    DateTime businessEndDateTime;
    DateTime startDateTime = DateTime.newInstance(startDate.year(), startDate.month(), startDate.day());

    BusinessHours bh = [SELECT Id,Name,IsActive,IsDefault,MondayEndTime,MondayStartTime 
                        FROM BusinessHours 
                        WHERE Name = 'US Business Hours'];
    businessEndDateTime = BusinessHours.add(bh.Id, startDateTime, businessDays*9*60*60*1000L);

    String strDateValue = businessEndDateTime.format().split('\\s+')[0];
    String[] strArray = strDateValue.split('/');

    return Date.newInstance(Integer.valueOf(strArray[1]), Integer.valueOf(strArray[0]), Integer.valueOf(strArray[2]));
}