iOS 时间类经常用法

//当前日前日期

NSDate *today = [NSDate
date];

//时区

NSTimeZone *zone = [NSTimeZone
systemTimeZone];

//设置间隔

_interval = [zone
secondsFromGMTForDate: today];

//今天+8小时（中国上海时区）

today = [today 
dateByAddingTimeInterval:
_interval];

//获取明天日期

NSDate *tomorrowDate = [[NSDate
*
*
sinceDate:[NSDate
date]];

//日历

NSCalendar *calendar = [NSCalendar
currentCalendar];

//comps里能够分离出时间年月日等信息

NSDateComponents *comps = [calendar
components:(NSYearCalendarUnit |
NSMonthCalendarUnit |
NSDayCalendarUnit |
NSWeekCalendarUnit |
NSWeekdayCalendarUnit |NSWeekdayOrdinalCalendarUnit |
NSHourCalendarUnit) fromDate:tomorrowDate];

//获取当前星期几

NSInteger weekday = [comps
weekday];

//将NSString类型转换成NSDate

NSDate *serverDate = [dateFomatter
dateFromString:serverTimeStr];

NSDate *createDate = [dateFomatter
dateFromString:createTimeStr];

//算出两个Date的间隔

NSTimeInterval betweenTime = [serverDate
timeIntervalSinceDate:createDate];

   //分离出标准格式里的年月日时分秒  

NSDateFormatter *dateFomatter = [[NSDateFormatter
alloc]init];

[dateFomatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

//将string换成formatter形式

NSDate *stringDate = [dateFomatter
dateFromString:string];

//formatter为月和日

[dateFomatter
setDateFormat:@"MM-dd"];

//提取字符串中月和日

NSString *str1 = [dateFomatter
stringFromDate:stringDate];