convert a RFC3339 string to an NSDate you can use dateFromRFC3339String

gistfile1.m

+ (NSDate *)dateFromRFC3339String:(NSString *)dateString
{
    NSDate *date = nil;
    if (dateString) {
        NSDateFormatter *dateFormatter = [self internetDateTimeFormatter];

        NSString *RFC3339String = [[NSString stringWithString:dateString] uppercaseString];
        RFC3339String = [RFC3339String stringByReplacingOccurrencesOfString:@"Z" withString:@"-0000"];
        if (RFC3339String.length > 20) {
            RFC3339String = [RFC3339String stringByReplacingOccurrencesOfString:@":"
                                                                     withString:@""
                                                                        options:0
                                                                          range:NSMakeRange(20, RFC3339String.length-20)];
        }
        if (!date) { // 1937-01-01T12:00:27
            [dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss"];
            date = [dateFormatter dateFromString:RFC3339String];
        }
        if (!date) { // 1996-12-19T16:39:57-0800
            [dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ssZZZ"];
            date = [dateFormatter dateFromString:RFC3339String];
        }
        if (!date) { // 1937-01-01T12:00:27.87+0020
            [dateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss.SSSZZZ"];
            date = [dateFormatter dateFromString:RFC3339String];
        }
        if (!date) DLog(@"Could not parse RFC3339 date: \"%@\" Possible invalid format.", dateString);

    }

    return date;
}

+ (NSDateFormatter *)internetDateTimeFormatter
{
    NSLocale *en_US_POSIX = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
    NSDateFormatter *internetDateTimeFormatter = [[NSDateFormatter alloc] init];
    [internetDateTimeFormatter setLocale:en_US_POSIX];
    [internetDateTimeFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
    return internetDateTimeFormatter;
}