gistfile3.m

//
//  NSDateRFC1123TC.m
//  Filmfest
//
//  Created by Marcus Rohrmoser on 19.08.09.
//  Copyright 2009 __MyCompanyName__. All rights reserved.
//

#import "LogicTC.h"
#import "NSDateRFC1123.h"

/**
 http://blog.mro.name/2009/08/nsdateformatter-http-header/ and
 http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1
 */
@interface NSDateRFC1123TC : LogicTC
{

}


@end

@implementation NSDateRFC1123TC

-(void)testAsctime
{
    STAssertEqualObjects(@"Sun, 06 Nov 1994 08:49:37 GMT", [[NSDate dateFromRFC1123:@"Sun Nov  6 08:49:37 1994"] rfc1123String], @"fail");
    STAssertEqualObjects(@"Wed, 16 Nov 1994 08:49:37 GMT", [[NSDate dateFromRFC1123:@"Wed Nov 16 08:49:37 1994"] rfc1123String], @"fail");
}


-(void)testRFC850
{
    STAssertEqualObjects(@"Sun, 06 Nov 1994 08:49:37 GMT", [[NSDate dateFromRFC1123:@"Sunday, 06-Nov-94 08:49:37 GMT"] rfc1123String], @"fail");
}


-(void)testRFC1123
{
    NSString *s = @"Fri, 14 Aug 2009 14:45:31 GMT";
    STAssertEqualObjects(s, [[NSDate dateFromRFC1123:s] rfc1123String], @"fail");

    s = @"Sun, 06 Nov 1994 08:49:37 GMT";
    STAssertEqualObjects(s, [[NSDate dateFromRFC1123:s] rfc1123String], @"fail");

    STAssertEqualObjects(@"Sun, 06 Nov 1994 07:49:37 GMT",
        [[NSDate dateFromRFC1123:@"SUN, 06 Nov 1994 08:49:37 CET"] rfc1123String], @"fail");

    STAssertEqualObjects(@"Sun, 06 Nov 1994 07:49:37 GMT",
        [[NSDate dateFromRFC1123:@"Sunday, 06 Nov 1994 08:49:37 CET"] rfc1123String], @"fail");

    STAssertEqualObjects(@"Sun, 06 Nov 1994 07:49:37 GMT",
        [[NSDate dateFromRFC1123:@"Sun, 06 Nov 1994 08:49:37 CET"] rfc1123String], @"fail");

//	a strange asymmetry:
    STAssertEqualObjects(@"Sat, 01 Jan 0001 01:27:48 GMT",
        [[NSDate dateFromRFC1123:@"Sat, 01 Jan 0001 00:00:00 GMT"] rfc1123String], @"fail");
}


-(void)testRFC1123Mismatch
{
    STAssertNil([NSDate dateFromRFC1123:nil], @"fail");
    STAssertNil([NSDate dateFromRFC1123:@"Hello, world!"], @"fail");

    STAssertNil([NSDate dateFromRFC1123:@"Fru, 14 Aug 2009 14:45:31 GMT"], @"fail");
    STAssertNil([NSDate dateFromRFC1123:@"Fri, 29 Feb 2009 14:45:31 GMT"], @"fail");

    STAssertNil([NSDate dateFromRFC1123:@"Sunday, 06-Nov-94 08:49:37 FOO"], @"fail");

    STAssertNil([NSDate dateFromRFC1123:@"Sunda, 06-Nov-94 08:49:37 GMT"], @"fail");
}


-(void)testRawRFC1123
{
    NSDateFormatter *rfc1123 = [[NSDateFormatter alloc] init];
    rfc1123.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease];
    rfc1123.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
    rfc1123.dateFormat = @"EEE',' dd MMM yyyy HH':'mm':'ss 'GMT'";

    NSString *s = @"Fri, 14 Aug 2009 14:45:31 GMT";
    STAssertEqualObjects(s, [rfc1123 stringFromDate:[rfc1123 dateFromString:s]], @"fail");

    s = @"Sun, 06 Nov 1994 08:49:37 GMT";
    STAssertEqualObjects(s, [rfc1123 stringFromDate:[rfc1123 dateFromString:s]], @"fail");

    s = @"Sat, 01 Jan 0001 08:00:00 GMT";
    STAssertEqualObjects(s, [rfc1123 stringFromDate:[rfc1123 dateFromString:s]], @"fail");

    s = @"Sat, 01 Jan 0001 08:00:00 GMT";
    STAssertEqualObjects(s, [rfc1123 stringFromDate:[rfc1123 dateFromString:s]], @"fail");

    [rfc1123 release];
}


@end

NSDateRFC1123.h

//
//  NSDateRFC1123.h
//  Filmfest
//
//  Created by Marcus Rohrmoser on 19.08.09.
//  Copyright 2009 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.h>

/** Category on NSDate to add rfc1123 dates. Donated from the Filmfest App for free use as in free beer.
 http://blog.mro.name/2009/08/nsdateformatter-http-header/ and
 http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1
 */
@interface NSDate (NSDateRFC1123)

/**
 Convert a RFC1123 'Full-Date' string (http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1) into NSDate.
 @param value_ something like either @"Fri, 14 Aug 2009 14:45:31 GMT" or @"Sunday, 06-Nov-94 08:49:37 GMT" or @"Sun Nov  6 08:49:37 1994"
 @return nil if not parseable.
 */
+(NSDate*)dateFromRFC1123:(NSString*)value_;

/**
 Convert NSDate into a RFC1123 'Full-Date' string (http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3.1).
 @return something like @"Fri, 14 Aug 2009 14:45:31 GMT"
 */
-(NSString*)rfc1123String;

@end

NSDateRFC1123.m

//
//  NSDateRFC1123.m
//  Filmfest
//
//  Created by Marcus Rohrmoser on 19.08.09.
//  Copyright 2009 __MyCompanyName__. All rights reserved.
//

#import "NSDateRFC1123.h"

@implementation NSDate (NSDateRFC1123)

+(NSDate*)dateFromRFC1123:(NSString*)value_
{
    if(value_ == nil)
        return nil;
    static NSDateFormatter *rfc1123 = nil;
    if(rfc1123 == nil)
    {
        rfc1123 = [[NSDateFormatter alloc] init];
        rfc1123.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease];
        rfc1123.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
        rfc1123.dateFormat = @"EEE',' dd MMM yyyy HH':'mm':'ss z";
    }
    NSDate *ret = [rfc1123 dateFromString:value_];
    if(ret != nil)
        return ret;

    static NSDateFormatter *rfc850 = nil;
    if(rfc850 == nil)
    {
        rfc850 = [[NSDateFormatter alloc] init];
        rfc850.locale = rfc1123.locale;
        rfc850.timeZone = rfc1123.timeZone;
        rfc850.dateFormat = @"EEEE',' dd'-'MMM'-'yy HH':'mm':'ss z";
    }
    ret = [rfc850 dateFromString:value_];
    if(ret != nil)
        return ret;

    static NSDateFormatter *asctime = nil;
    if(asctime == nil)
    {
        asctime = [[NSDateFormatter alloc] init];
        asctime.locale = rfc1123.locale;
        asctime.timeZone = rfc1123.timeZone;
        asctime.dateFormat = @"EEE MMM d HH':'mm':'ss yyyy";
    }
    return [asctime dateFromString:value_];
}


-(NSString*)rfc1123String
{
    static NSDateFormatter *df = nil;
    if(df == nil)
    {
        df = [[NSDateFormatter alloc] init];
        df.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"] autorelease];
        df.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
        df.dateFormat = @"EEE',' dd MMM yyyy HH':'mm':'ss 'GMT'";
    }
    return [df stringFromDate:self];
}


#if 0
// Fri, 14 Aug 2009 14:45:31 GMT
NSLogD(@"Last-Modified: %@", [vc.response.allHeaderFields objectForKey:@"Last-Modified"]);
//		df.calendar = @"gregorian";
NSLogD(@"Now: %@", [NSDate date]);
for(NSString* fmt in [NSArray arrayWithObjects:@"a", @"b", @"c", @"d", @"e", @"f", @"g", @"h", @"i", @"j", @"k", @"l", @"m", @"n", @"o", @"p", @"q", @"r", @"s", @"t", @"u", @"v", @"w", @"x", @"y", @"z", nil])
{
    rfc1123.dateFormat = [NSString stringWithFormat:@"%@%@%@", fmt, fmt, fmt];
    rfc1123.dateFormat = fmt;
    NSLogD(@"Now (%@): %@", rfc1123.dateFormat, [rfc1123 stringFromDate:[NSDate date]]);
    rfc1123.dateFormat = [rfc1123.dateFormat uppercaseString];
    NSLogD(@"Now (%@): %@", rfc1123.dateFormat, [rfc1123 stringFromDate:[NSDate date]]);
}
#endif

@end

I forked this for a project and updated it to use ARC.

I also fixed some broken tests and tried to make it recognize more timezones.

https://gist.github.com/yjkogan/7885169