Why Does Java SimpleDateFormat Convert AD Dates to January (yyyy/MM/DD vs yyyy/MM/dd)?

Java SimpleDateFormat Conundrum: All Months Default to January

When parsing dates from Active Directory using Java's SimpleDateFormat, a puzzling issue arises: every single date is erroneously converted to January. Intrigued by this discrepancy, let's delve into a code snippet that exemplifies the problem:

<code class="java">private Date getParsedDate(String givenString) {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/DD");
    try {
        return sdf.parse(formattedString);
    } catch (ParseException ex) {
        ex.printStackTrace();
    }
    return null;
}</code>

upon executing this code with the AD date value "20050912190509.0Z", we obtain the unexpected output:

Value from AD is: 20050912190509.0Z
Formatted String is: 2005/09/12
Final date string is: Wed Jan 12 00:00:00 EST 2005

While the day and year are accurately identified, the month is persistently mistaken for January. What secret lies within this seemingly straightforward code that leads to this glaring error?

The answer lies in a subtle oversight in the SimpleDateFormat pattern string. By specifying "yyyy/MM/DD", we inadvertently force the month format to be in upper case letters "MM". However, the Active Directory date value uses lowercase "mm" for months.

To rectify this issue, we simply adjust the pattern string to "yyyy/MM/dd" with lowercase "dd" for days:

<code class="java">SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd");</code>

By making this minor modification, the SimpleDateFormat correctly interprets the dates from Active Directory, rendering the final date string with the correct month:

Value from AD is: 20050912190509.0Z
Formatted String is: 2005/09/12
Final date string is: Wed Sep 12 00:00:00 EST 2005

This correction ensures that Java's SimpleDateFormat accurately parses dates from Active Directory, enabling you to confidently work with historical data or create reports based on specific date ranges.

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