[转]使用 NSDate,NSCalendar, NSDateComponents 获得时间之差总结

原文：　http://blog.csdn.net/JHorn/archive/2009/09/27/4602491.aspx
方法一

NSDate* toDate1 = [ [ NSDate alloc] initWithString:@"2520-9-26 17:10:00 +0600" ];

NSTimeInterval distance = [ toDate1 timeIntervalSinceNow  ];

NSTimeInterval iDat = distance / ( 86400 ) ;

NSLog( @" From now to %@ diff: %f ", [toDate1 description ], iDat  );

[ toDate1 release ];

方法二

NSDate* toDate	 = [ [ NSDate alloc] initWithString:@"2009-9-29 0:0:00 +0600" ];

NSDate*  startDate	= [ [ NSDate alloc] init ];

NSCalendar* chineseClendar = [ [ NSCalendar alloc ] initWithCalendarIdentifier:NSGregorianCalendar ];

NSUInteger unitFlags =	NSHourCalendarUnit | NSMinuteCalendarUnit | 

NSSecondCalendarUnit | NSDayCalendarUnit

| NSMonthCalendarUnit | NSYearCalendarUnit;

NSDateComponents *cps = [ chineseClendar components:unitFlags fromDate:startDate  toDate:toDate  options:0];

NSInteger diffHour = [ cps hour ];

NSInteger diffMin    = [ cps minute ];

NSInteger diffSec   = [ cps second ];

NSInteger diffDay   = [ cps day ];

NSInteger diffMon  = [ cps month ];

NSInteger diffYear = [ cps year ];

NSLog(  @" From Now to %@, diff: Years: %d  Months: %d, Days; %d, Hours: %d, Mins:%d, sec:%d", 

[toDate description], diffYear, diffMon, diffDay, diffHour, diffMin,diffSec );

[ toDate release ];

[ startDate release ];

[ chineseClendar release ];