Adding a date time field value within a node programmatically
[0] =&gt; Array
                            (
                                [value] =&gt; 2012-11-27 09:38:00
                                [timezone] =&gt; America/Phoenix
                                [timezone_db] =&gt; America/Phoenix
                                [date_type] =&gt; datetime
                            )


As seen above,
the error was occuring due to improper date format So when I changed the date format to  date(Y-m-d\TH:i:s, REQUEST_TIME);
the $download_node-&gt;field_download_time['und'][]['value'] did not gave any error .