iOS中获取系统时间

NSDate * date = [NSDate date];
NSTimeInterval sec = [date timeIntervalSinceNow];
NSDate * currentDate = [[NSDate alloc] initWithTimeIntervalSinceNow:sec];

//设置时间输出格式：
NSDateFormatter * df = [[NSDateFormatter alloc] init ];
[df setDateFormat:@"yyyy年MM月dd日 HH小时mm分ss秒"];
NSString * na = [df stringFromDate:currentDate];

NSLog(@"系统当前时间为：%@",na);

//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];

NSLog(@"系统当前日期为：%@",nsDateString);