NSString 和 NSDate的转换

NSString *st1 = @"1988-08-09";

NSString *st2 = @"2013-11-11";

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

[format setDateFormat:@"yyyy-MM-dd"];

NSDate *d1 = [format dateFromString:st1];

NSDate *d2 = [format dateFromString:st2];

NSString *ss =[format stringFromDate:d1];

NSLog(@"天数功%lf",   [d2 timeIntervalSinceDate:d1]/24/1000);

NSLog(@"%@",ss);  //全世界的标准时间。格林时间