Fun with NSDate

dateTest.m

#import <Foundation/Foundation.h>

// clang -g -fobjc-arc -Wall -framework Foundation -o dateTest dateTest.m

@interface DateTest : NSObject
@end


@implementation DateTest

int main (void) {
	
	{
		NSLog(@"Creating a NSDate object...");

		NSDateComponents *components = [[NSDateComponents alloc] init];
		[components setYear:2012];
		[components setMonth:12];
		[components setDay:24];
		[components setHour:23];
		[components setMinute:42];
		[components setSecond:5];

		NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
		NSDate *christmas = [gregorian dateFromComponents:components];

		NSLog(@"Woohoo! Christmas time: %@", christmas);
	}

	{
		NSLog(@"Calendar fun...");

		NSDateComponents *components = [[NSDateComponents alloc] init];
		[components setYear:2012];
		[components setMonth:12];
		[components setDay:24];
		[components setHour:23];
		[components setMinute:42];
		[components setSecond:5];

		NSCalendar *currentCalendar = [NSCalendar currentCalendar];
		NSCalendar *japaneseCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSJapaneseCalendar];
		NSCalendar *buddhistCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSBuddhistCalendar];

		NSDate *currentChristmas = [currentCalendar dateFromComponents:components];
		NSDate *japaneseChristmas = [japaneseCalendar dateFromComponents:components];
		NSDate *buddhistChristmas = [buddhistCalendar dateFromComponents:components];

		NSLog(@"Current Christmas:\t%@", currentChristmas);
		NSLog(@"Japanese Christmas:\t%@", japaneseChristmas);
		NSLog(@"Buddhist Christmas:\t%@", buddhistChristmas);
	}

	{
		NSLog(@"Time Zone fun...");

		NSDateComponents *components = [[NSDateComponents alloc] init];
		[components setYear:2012];
		[components setMonth:12];
		[components setDay:24];
		[components setHour:23];
		[components setMinute:42];
		[components setSecond:5];

		NSCalendar *usersCalendar = [[NSLocale currentLocale] objectForKey:NSLocaleCalendar];
		NSDate *date = [usersCalendar dateFromComponents:components];

		NSString *dateFormat = @"dd.MM.yyyy G 'at' HH:mm:ss Z";
		NSDateFormatter *formatterPDT = [[NSDateFormatter alloc] init];
		[formatterPDT setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"PDT"]];
		[formatterPDT setDateFormat:dateFormat];
		NSDateFormatter *formatterUTC = [[NSDateFormatter alloc] init];
		[formatterUTC setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
		[formatterUTC setDateFormat:dateFormat];
		NSDateFormatter *formatterCET = [[NSDateFormatter alloc] init];
		[formatterCET setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"CET"]];
		[formatterCET setDateFormat:dateFormat];
		NSDateFormatter *formatterJST = [[NSDateFormatter alloc] init];
		[formatterJST setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"JST"]];
		[formatterJST setDateFormat:dateFormat];

		NSArray *formatters = @[formatterPDT, formatterUTC, formatterCET, formatterJST];
		for (NSDateFormatter *formatter in formatters) {
			NSLog(@"%@", [formatter stringFromDate:date]);
		}
	}
}

@end


#ifdef OUTPUT

> ./dateTest
dateTest[836:707] Creating a NSDate object...
dateTest[836:707] Woohoo! Christmas time: 2012-12-24 22:42:05 +0000

dateTest[836:707] Calendar fun...
dateTest[836:707] Current Christmas:	2012-12-24 22:42:05 +0000
dateTest[836:707] Japanese Christmas:	4000-12-24 22:42:05 +0000
dateTest[836:707] Buddhist Christmas:	1469-12-24 22:48:37 +0000

dateTest[836:707] Time Zone fun...
dateTest[836:707] 24.12.2012 AD at 14:42:05 -0800
dateTest[836:707] 24.12.2012 AD at 22:42:05 +0000
dateTest[836:707] 24.12.2012 AD at 23:42:05 +0100
dateTest[836:707] 25.12.2012 AD at 07:42:05 +0900

#endif