NSDate

//获得系统时间
NSDate * senddate=[NSDate date];
NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
[dateformatter setDateFormat:@"HH:mm"];
NSString * locationString=[dateformatter stringFromDate:senddate];
//[dateformatter setDateFormat:@"YYYY-MM-dd-HH-mm-ss"];
//NSString * morelocationString=[dateformatter stringFromDate:senddate];

当前时间几天后的时间
NSDate date = [NSDate dateWithTimeIntervalSinceNow:(indexPath.row+1)246060];
NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
[dateformatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"];
NSString *morelocationString=[dateformatter stringFromDate:date];

//获得系统日期
NSCalendar * cal=[NSCalendar currentCalendar];
NSUInteger unitFlags=NSDayCalendarUnit|NSMonthCalendarUnit|NSYearCalendarUnit;
NSDateComponents * conponent= [cal components:unitFlags fromDate:senddate];
NSInteger year=[conponent year];
NSInteger month=[conponent month];
NSInteger day=[conponent day];
NSString * nsDateString= [NSString stringWithFormat:@"M年-月-日",year,month,day];
[dateformatter release];

2. 从字符串来获得NSDate
   string strYear="1988";
   string strMonth="09";
   string strDay="18";
   string strHour="5";
   string strMinutes="18";
   string strSec="20";
   morelocationString=[NSString stringWithFormat:@"%s-%s-%s-%s-%s-%s",strYear.c_str(),strMonth.c_str(),
   strDay.c_str(),strHour.c_str(),strMinutes.c_str(),strSec.c_str()];

//根据时间字符串获得NSDate
NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
[dateformatter setDateFormat:@"YYYY-MM-dd-HH-mm-ss"];
NSDate * oldDate=[dateformatter dateFromString:morelocationString];

3. 从GMT时间，得到本地时间
   NSDate * oldDate=[dateformatter dateFromString:morelocationString];
   NSTimeInterval timeZoneOffset=[[NSTimeZone systemTimeZone] secondsFromGMT];
   NSDate * newDate=[oldDate dateByAddingTimeInterval:timeZoneOffset];