How to properly convert the Last-Modified header from an HTTP response to an NSDate on iOS

I am looking for a fully working solution, one that works with:

• any iOS locale or timezone
• any/most HTTP servers
• Xcode 4.0.2 (see why)

Current broken code:

 NSString lastModifiedString = @"Mon, 06 Jun 2011 12:47:05 GMT";
 NSDateFormatter *df = [[NSDateFormatter alloc] init];  
 //df.dateFormat = @"EEE',' dd MMM yyyy HH':'mm':'ss 'GMT'";
 df.dateFormat = @"EEE, dd MMM yyyy HH:mm:ss z";
 df.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];  
 df.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];  
 NSDate date = [df dateFromString:lastModifiedString];  

I assumed that Last-Modifie开发者_开发知识库d is supposed to use the same format like other date fields in HTTP spec, meaning to use RFC-1123 / RFC-822

Resources:

• http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html HTTP 1.1
• http://developer.apple.com/library/ios/#qa/qa1480/_index.html

The only thing wrong is that you're missing asterisks in-between NSString and lastModifiedString, and also between NSDate and date. Once you put those in, this code works for me.