NSDate日期操作

        NSDate * date = [NSDate date];
        NSLog(@"获取当前日期：%@",date);
        
        //dateByAddingTimeInterval获取其他日期
        NSTimeInterval timeInterval = 24 * 60 * 60;
        NSDate * newDate = [date dateByAddingTimeInterval:timeInterval];
        NSLog(@"新的时间为：%@",newDate);
        
        //earlierDate获取两个时间中较早的时间
        NSDate * earlyDate = [date earlierDate:newDate];
        NSLog(@"两个时间中较早的时间为：%@",earlyDate);
        
        //laterDate获取两个时间中较晚的时间
        NSDate * laterDate = [date laterDate:newDate];
        NSLog(@"两个时间中较晚的时间为：%@",laterDate);
        
        //isEqualToDate比较两个时间是否相等
        BOOL isEqual = [date isEqualToDate:newDate];
        if (isEqual) {
            NSLog(@"两个时间相等");
        }else{
            NSLog(@"两个时间不相等");
        }
        
        //格式化日期
        NSDateFormatter * formatter = [[NSDateFormatter alloc] init];
        [formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
        [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
        NSString * dateStr = [formatter stringFromDate:date];
        NSLog(@"格式化后的日期：%@",dateStr);
        
        //将字符串转成日期
        NSString * dateString = @"1991-1-2 12:24:48";
        NSDate * strToData = [formatter dateFromString:dateString];
        NSLog(@"转换后的日期：%@",strToData);