NSDate * senddate=[NSDate date];
NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
[dateformatter setDateFormat:@"YYYYMMdd"];
NSString * locationString=[dateformatter stringFromDate:senddate];
NSLog(@"locationString:%@",locationString);
[dateformatter release];
格式：YYYY-MM-dd HH:mm:ss
