Sort NSArray by date and time

This may be a duplicate question, but i have a strange issue, So that i have pasted it on stack.

I have a issue while sorting NSArray by date and time.

For example, I have below fields in Database file:-

id        Name       Date
1         ABC        2015-01-29 16:36:31
2         AAA        2015-01-29 16:36:31
3         BBB        2015-01-29 16:36:31
4         CCC        2015-01-29 16:36:31
5         DDD        2015-01-29 16:36:31

Note :- Datatype of Date filed is Timestamp in sqlite Database and i am storing it as NSDate while fetching data.

Now, I am sorting this data as below through NSArray

NSSortDescriptor *sortDesc = [[NSSortDescriptor alloc]initWithKey:kContentEditedDate ascending:NO];
        NSArray *sortDescAry = [NSArray arrayWithObject:sortDesc];
        contentData = [contentData sortedArrayUsingDescriptors:sortDescAry];

Above code just display descending order even each row has same date.

After that i also tried [NSArray sortedArrayUsingComparator:] to sorting it also display same result as first option.

I search a lot but didn't get any proper solution for it.