Objective-C日期NSDate使用

NSDate *firstDate = [NSDate date];
    NSLog(@"firstDate:%@",firstDate);
    NSDate *secondDate = [[NSDate date] initWithTimeIntervalSinceNow:120];
    NSLog(@"secondDate:%@",secondDate);
    NSLog(@"earlierDate:%@",[secondDate earlierDate:firstDate]);
    NSDate *threeDate = [[NSDate date] initWithTimeInterval:38 sinceDate:firstDate];
    NSLog(@"===%@,***%@,---%@",firstDate,secondDate,threeDate);
    NSLog(@"%@",[NSDate now]);
    NSLog(@"%f",[[NSDate date] timeIntervalSince1970]);
    
    NSDate *df_date = [NSDate distantFuture];
    NSDate *dp_date = [NSDate distantPast];
    NSLog(@"distantFuture:%@,distantPast:%@",df_date,dp_date);
    NSLog(@"earlierDate:%@",[df_date earlierDate:dp_date]);
    NSLog(@"laterDate:%@",[df_date laterDate:dp_date]);
    NSDateFormatter *fmt = [[NSDateFormatter alloc]init];
    NSLog(@"系统默认时区:%@",[NSTimeZone systemTimeZone]);
    //[fmt setTimeZone:[NSTimeZone systemTimeZone]];
    [fmt setTimeZone:[NSTimeZone timeZoneWithName:@"Asia/Shanghai"]];
    //[fmt setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:28800]];
    [fmt setDateFormat:@"yyyy年MM月dd日 HH时mm分ss秒SSS毫秒"];
    NSLog(@"系统时间:%@",[fmt stringFromDate:[NSDate date]]);
    //时间戳转日期
    NSDate *tmpDate = [NSDate dateWithTimeIntervalSince1970:1705076347];
    NSString *strDate = [fmt stringFromDate:tmpDate];
    NSLog(@"时间戳转日期:%@",strDate);