gen_json.rb

#!/usr/bin/env ruby
require 'time'

def time_rand from = 0.0, to = Time.now
  Time.at(from + rand * (to.to_f - from.to_f))
end

num_iterations = 3000
dates = []
i = 0
while i < num_iterations
    d = time_rand
    dates << d
    i += 1
end

File.open("iso8601.json", 'w:UTF-8') do |f|
    f.puts "{"
    f.puts '    "dates" : ['
    i = 0
    while i < num_iterations
        date = dates[i]
        f.write "        \"#{date.utc.iso8601}\""
        if i < num_iterations - 1
            f.write ","
        end
        f.write "\n"
        i += 1
    end
    f.puts "    ]"
    f.puts "}"
end

File.open("objects.json", 'w:UTF-8') do |f|
    f.puts "{"
    f.puts '    "dates" : ['
    i = 0
    while i < num_iterations
        date = dates[i]
        f.puts  "        {"
        f.write "            \"timeEpochSeconds\" : "
        f.write "#{date.to_i},\n"
        f.write "            \"timeZoneOffsetSeconds\" : -21600,\n"
        f.write "            \"timeZoneName\" : \"America/Chicago\",\n"
        f.write "            \"isDST\" : true\n"
        f.write "        }"
        if i < num_iterations - 1
            f.write ","
        end
        f.write "\n"
        i += 1
    end
    f.puts "    ]"
    f.puts "}"
end

results.txt

NSDateFormatter Total Time: 760ms
NSDateFormatter per Iteration: 248832ns
NSDateFormatter JSON Parse Time: 10ms
NSDateFormatter Creation Time: 3ms
Objects Total Time: 281ms
Objects per Iteration: 11154ns
Objects JSON Parse Time: 248ms

SCRandomTimingViewController.m

//
//  SCTimingViewController.m
//  iOSTester
//
//  Created by Sebastian Celis on 8/6/12.
//

#import <mach/mach.h>
#import <mach/mach_time.h>
#import "SCTimingViewController.h"

#define kNumIterations 3000
#define kNanosecondsPerMillisecond 1000000
#define kNanosecondsPerSecond 1000000000

@implementation SCTimingViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    [self setTitle:@"Timing"];
    [[self view] setBackgroundColor:[UIColor whiteColor]];
    
    NSMutableString *str = [[NSMutableString alloc] init];
        
    // Get timebase information.
    uint64_t start, end, elapsed, elapsedNanos;
    mach_timebase_info_data_t timebase;
    mach_timebase_info(&timebase);
    
    // Date Parsing
    NSMutableArray *dates1 = [NSMutableArray array];
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"iso8601" ofType:@"json"];
    NSData *data = [[NSData alloc] initWithContentsOfFile:filePath];
    start = mach_absolute_time();
    NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:0 error:NULL];
    uint64_t parse1 = mach_absolute_time();
    NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
    [formatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease]];
    [formatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ss'Z'"];
    uint64_t formatter1 = mach_absolute_time();
    for (NSString *dateString in [dict objectForKey:@"dates"])
    {
        [dates1 addObject:[formatter dateFromString:dateString]];
    }    
    end = mach_absolute_time();
    elapsed = end - start;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"NSDateFormatter Total Time: %lldms\n", elapsedNanos / kNanosecondsPerMillisecond];
    
    elapsed = end - formatter1;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"NSDateFormatter per Iteration: %lldns\n", elapsedNanos / kNumIterations];
    
    elapsed = parse1 - start;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"NSDateFormatter JSON Parse Time: %lldms\n", elapsedNanos / kNanosecondsPerMillisecond];
    
    elapsed = formatter1 - parse1;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"NSDateFormatter Creation Time: %lldms\n", elapsedNanos / kNanosecondsPerMillisecond];
        
    // Object Parsing
    NSMutableArray *dates2 = [NSMutableArray array];
    NSMutableArray *zones2 = [NSMutableArray array];
    NSMutableArray *offsets2 = [NSMutableArray array];
    NSMutableArray *isDST2 = [NSMutableArray array];
    filePath = [[NSBundle mainBundle] pathForResource:@"objects" ofType:@"json"];
    data = [[NSData alloc] initWithContentsOfFile:filePath];
    start = mach_absolute_time();
    dict = [NSJSONSerialization JSONObjectWithData:data options:0 error:NULL];
    uint64_t parse2 = mach_absolute_time();
    for (NSDictionary *dateDict in [dict objectForKey:@"dates"])
    {
        [dates2 addObject:[NSDate dateWithTimeIntervalSince1970:[[dateDict objectForKey:@"timeEpochSeconds"] doubleValue]]];
        [zones2 addObject:[dateDict objectForKey:@"timeZoneName"]];
        [offsets2 addObject:[dateDict objectForKey:@"timeZoneOffsetSeconds"]];
        [isDST2 addObject:[dateDict objectForKey:@"isDST"]];
    }
    end = mach_absolute_time();
    elapsed = end - start;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"Objects Total Time: %lldms\n", elapsedNanos / kNanosecondsPerMillisecond];
    
    elapsed = end - parse2;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"Objects per Iteration: %lldns\n", elapsedNanos / kNumIterations];
    
    elapsed = parse2 - start;
    elapsedNanos = (elapsed * (timebase.numer / timebase.denom));
    [str appendFormat:@"Objects JSON Parse Time: %lldms\n", elapsedNanos / kNanosecondsPerMillisecond];
    
    // Display results.
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectInset([[self view] bounds], 10.0, 10.0)];
    [label setAutoresizingMask:UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight];
    [label setFont:[UIFont systemFontOfSize:12.0]];
    [label setNumberOfLines:0];
    [label setLineBreakMode:UILineBreakModeWordWrap];
    [label setText:str];
    [str release];
    [[self view] addSubview:label];
    [label release];
    
    NSLog(@"%d %d %d %d %d", [dates1 count], [dates2 count], [zones2 count], [offsets2 count], [isDST2 count]);
    NSLog(@"%@", [label text]);
}

@end

SCTimingViewController.h

//
//  SCTimingViewController.h
//  iOSTester
//
//  Created by Sebastian Celis on 8/6/12.
//

#import <UIKit/UIKit.h>

@interface SCTimingViewController : UIViewController

@end