［转载］ios 如何获得系统时间和日期

//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];  

  

//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:@"%4d年%2d月%2d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];