日時オブジェクトから年月日や時分秒、曜日をとりだしたい

iphone objective-c nsdate 
NSDate *date = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *comps;

// 年月日をとりだす
comps = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) 
					fromDate:date];
NSInteger year = [comps year];
NSInteger month = [comps month];
NSInteger day = [comps day];
NSLog(@"year: %d month: %d, day: %d", year, month, day);
//=> year: 2010 month: 5, day: 22

// 時分秒をとりだす
comps = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit)
					fromDate:date];
NSInteger hour = [comps hour];
NSInteger minute = [comps minute];
NSInteger second = [comps second];
NSLog(@"hour: %d minute: %d second: %d", hour, minute, second);
//=> hour: 18 minute: 24 second: 31

// 週や曜日などをとりだす
comps = [calendar components:(NSWeekCalendarUnit | NSWeekdayCalendarUnit | NSWeekdayOrdinalCalendarUnit)
					fromDate:date];
NSInteger week = [comps week]; // 今年に入って何週目か
NSInteger weekday = [comps weekday]; // 曜日
NSInteger weekdayOrdinal = [comps weekdayOrdinal]; // 今月の第何曜日か
NSLog(@"week: %d weekday: %d weekday ordinal: %d", week, weekday, weekdayOrdinal);
//=> week: 21 weekday: 7(日曜日) weekday ordinal: 4(第4日曜日)

月日、時分秒を指定して日時オブジェクトを生成したい

iphone objective-c nsdate 
// 年月日、時分秒を指定して日時オブジェクトを生成する
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setYear:2010];
[comps setMonth:1];
[comps setDay:2];
[comps setHour:3];
[comps setMinute:4];
[comps setSecond:5];
NSDate *date = [calendar dateFromComponents:comps];
NSLog(@"date: %@", date); // => date: 2010-01-02 03:04:05 +0900

ふたつの日時の差を求めたい(年月日)

iphone objective-c nsdate 
// ふたつの日時の差を求める(年月日のみ)
NSCalendar *calendar = [NSCalendar currentCalendar];

NSDateComponents *comps1 = [[NSDateComponents alloc] init];
[comps1 setYear:2009];
[comps1 setMonth:3];
[comps1 setDay:10];
NSDate *date1 = [calendar dateFromComponents:comps1];

NSDateComponents *comps2 = [[NSDateComponents alloc] init];
[comps2 setYear:2010];
[comps2 setMonth:5];
[comps2 setDay:20];
NSDate *date2 = [calendar dateFromComponents:comps2];

NSDateComponents *diff = [calendar components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:date1 toDate:date2 options:0];

NSLog(@"Year: %d Month: %d Day: %d", [diff year], [diff month], [diff day]); // => Year: 1 Month: 2 Day: 10

ふたつの日時の差を求めたい(日時分)

iphone objective-c nsdate 
// ふたつの日時の差をもとめる(日時分のみ)
NSCalendar *calendar = [NSCalendar currentCalendar];

NSDateComponents *comps1 = [[NSDateComponents alloc] init];
[comps1 setYear:2010];
[comps1 setMonth:4];
[comps1 setDay:5];
[comps1 setHour:10];
[comps1 setMinute:30];
NSDate *date1 = [calendar dateFromComponents:comps1];

NSDateComponents *comps2 = [[NSDateComponents alloc] init];
[comps2 setYear:2010];
[comps2 setMonth:4];
[comps2 setDay:6];
[comps2 setHour:12];
[comps2 setMinute:45];
NSDate *date2 = [calendar dateFromComponents:comps2];

NSDateComponents *diff = [calendar components:(NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit) fromDate:date1 toDate:date2 options:0];

NSLog(@"Day: %d Hour: %d Minute: %d", [diff day], [diff hour], [diff minute]); // => Day: 1 Hour: 2 Minute: 15

n日後の日時を求めたい

iphone objectivce-c nsdae 
// n日後の日時をもとめる
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *now = [NSDate date];

NSDateComponents *sevenDays = [[NSDateComponents alloc] init];
[sevenDays setDay:7];

NSDate *sevenDaysLater = [calendar dateByAddingComponents:sevenDays toDate:now options:0];

NSLog(@"seven days later: %@", sevenDaysLater); // => seven days later: 2010-04-11 22:45:55

日時をフォーマット出力したい

iphone objective-c nsdate 
// 日時をフォーマット出力する
// 書式はここ http://unicode.org/reports/tr35/tr35-6.html#Date_Format_Patterns
NSDate *now = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd(E) HH:mm:ss"];
NSString *result = [formatter stringFromDate:now];
NSLog(@"Now: %@", result);

文字列から日時を生成したい

iphone objective-c nsdate 
// 文字列から日時を生成する
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm"];
NSDate *date = [formatter dateFromString:@"2010-7-8 13:14"];
NSLog(@"Date: %@", date);

ミリ秒単位でふたつの日時の差異を求めたい

iphone objective-c nsdate 
// ミリ秒単位のふたつの日時の差異を求めたい
NSDate *now = [NSDate date];
NSLog(@"now: %@", now);
for (int i=0; i<10; i++) {
	NSLog(@"delay!!");
}
NSDate *then = [NSDate date];
NSLog(@"then: %@", then);
NSLog(@"then - now: %1.3fsec", [then timeIntervalSinceDate:now]);