You've got your Date Format wrong for the style of Date you are passing in. Here is a document explaining the different modifiers: Date Format Patterns
To parse the Date "Sun Jul 17 07:48:34 +0000 2011", you'd need a Format like so:
[dateFormat setDateFormat:@"EEE MMM dd HH:mm:ss ZZZ yyyy"];
To get it into the following format: "2011-07-17 07:48:34", here is the full code:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"EEE MMM dd HH:mm:ss ZZZ yyyy"];
NSDate *date = [dateFormatter dateFromString:sDate];
// Convert to new Date Format
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSString *newDate = [dateFormatter stringFromDate:date];
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