Datetime Format Method not working as desired

Question

I came across a weird scenario. The format method is replacing month with '00' in its result.

A portion of my code: (Executed Anonymously to test)

System.Debug(logginglevel.error,'****m.date_approved__c***'+m.date_approved__c);

if(m.date_approved__c!=null) {
    System.Debug(logginglevel.error,'****year***'+m.date_approved__c.year());
    System.Debug(logginglevel.error,'****month***'+m.date_approved__c.month());
    System.Debug(logginglevel.error,'****day***'+m.date_approved__c.day());

    Datetime dt = DateTime.newInstance(m.date_approved__c.year(), m.date_approved__c.month(),m.date_approved__c.day());
    System.Debug(logginglevel.error,'****date before formatting***'+dt);

    approveddate = dt.Format('mm/dd/yyyy');
}

System.Debug(logginglevel.error,'****approveddate***'+approveddate);`

Debug Results

11:24:31.35 (85764301)|USER_DEBUG|[138]|ERROR|****m.date_approved__c***2016-06-24 00:00:00
11:24:31.35 (85826327)|USER_DEBUG|[140]|ERROR|****year***2016
11:24:31.35 (85873389)|USER_DEBUG|[141]|ERROR|****month***6
11:24:31.35 (85950679)|USER_DEBUG|[142]|ERROR|****day***24
11:24:31.35 (86109856)|USER_DEBUG|[144]|ERROR|****date before formatting***2016-06-24 07:00:00
11:24:31.35 (86188235)|USER_DEBUG|[149]|ERROR|****approveddate***00/24/2016

I tested this method separately, and it is working fine.

MyObj__c m = [select id, date_approved__c from MyObj__C WHERE Id = 'a033900000EU9LN'];
Datetime dt = DateTime.newInstance(m.date_approved__c.year(), m.date_approved__c.month(),m.date_approved__c.day());

System.Debug(logginglevel.error,'****date before formatting***'+dt);
System.Debug(logginglevel.error,'*****testing format method******'+dt.Format('MM/dd/yyyy'));`

Debug result:

11:27:41.1 (6791165)|USER_DEBUG|[3]|ERROR|****date before formatting***2016-06-24 07:00:00
11:27:41.1 (6886491)|USER_DEBUG|[4]|ERROR|*****testing format method******06/24/2016

I used the same record in both the cases

Any thoughts?

Answer 1

Look at Java SimpleDateFormat. These format strings are case-sensitive, as different casings of the same letter can have different meanings.

m outputs Minute in hour.

M outputs Month in year.

So make sure you use MM when trying to output the month, and only use mm if you are trying to output the minutes.

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SimpleDateFormat patterns

letter - description - type - example

• G - Era designator - Text - AD
• y - Year - Year - 1996; 96
• M - Month in year - Month - July; Jul; 07
• w - Week in year - Number - 27
• W - Week in month - Number - 2
• D - Day in year - Number - 189
• d - Day in month - Number - 10
• F - Day of week in month - Number - 2
• E - Day in week - Text - Tuesday; Tue
• a - Am/pm marker - Text - PM
• H - Hour in day (0-23) - Number - 0
• k - Hour in day (1-24) - Number - 24
• K - Hour in am/pm (0-11) - Number - 0
• h - Hour in am/pm (1-12) - Number - 12
• m - Minute in hour - Number - 30
• s - Second in minute - Number - 55
• S - Millisecond - Number - 978
• z - Time zone - General time zone - Pacific Standard Time; PST; GMT-08:00
• Z - Time zone - RFC 822 time zone - -0800