IOS中级篇 —— 日期时间对象

结合NSCalendar和NSDate能做更多的日期\时间处理 获得NSCalendar对象

NSCalendar *calendar = [NSCalendar currentCalendar];?获得年月日

- (NSDateComponents *)components:(NSCalendarUnit)unitFlags fromDate:(NSDate *)date;

//创建日期
NSDate?*d = [NSDate?date];

//创建日期对象
NSCalendar?*ca = [NSCalendar?currentCalendar];

//获得时间组件

NSDateComponents?*cms= [ca?components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay fromDate:d];

NSLog(@"%ld-%ld-%ld",cms.year,cms.month,cms.day);

比较两个日期的差距
- (NSDateComponents *)components:(NSCalendarUnit)unitFlags fromDate:(NSDate *) startingDate toDate:(NSDate *)resultDate options:(NSCalendarOptions)opts;

NSString *time1 =?@"2014-04-08 20:50:40"; NSString *time2 =?@"2014-04-04 18:45:30";

NSDateFormatter *fmt = [[NSDateFormatter alloc] init]; fmt.dateFormat =?@"yyyy-MM-dd HH:mm:ss";

// 1.创建一个日历对象
NSCalendar?*calendar = [NSCalendar?currentCalendar];

// 2.比较时间的差距
int?unit =?NSCalendarUnitYear?|?NSCalendarUnitMonth?|?NSCalendarUnitDay
|?NSCalendarUnitHour?|?NSCalendarUnitMinute?|?NSCalendarUnitSecond;?

NSDateComponents?*cmps = [calendar?components:unit?fromDate:date2?toDate:date1?options:0];

//2)昨天的现在
NSTimeInterval secondsPerDay1 = 24*60*60;

格式化日期

NSDate ----> dateString 

//定义NSDate
NSDate?*d1 = [NSDate?date];

//定义日期时间格式化的类
NSDateFormatter?*formatter = [[NSDateFormatter?alloc]?init]; formatter.dateFormat?=?@"yyyy-MM-dd HH:mm:ss";

//把Date转换为dataStr
NSString?*dateStr = [formatter?stringFromDate:d1];