时间与时间戳的转换

时间戳是一种时间表示，定义从格林尼治时间1970年01月01日00时00分00秒起至现在的总秒数
//现在时间
    NSDate *nowTime = [NSDate date];
    //获取时区
    NSTimeZone *zone = [NSTimeZone systemTimeZone];
    NSInteger interVal = [zone secondsFromGMTForDate:nowTime];
    NSDate *localTime = [nowTime dateByAddingTimeInterval:interVal];//本地时间
    //时间戳转为时间
    NSString *time = @"1400386922";
    CGFloat dTime = [time floatValue];

    NSDate *publishTime = [NSDate dateWithTimeIntervalSince1970:dTime];
    NSLog(@"%@", publishTime);
    
    //计算时间间隔(localTime - publishTime)
    NSTimeInterval timeInterval = [localTime timeIntervalSinceDate:publishTime];
    NSLog(@"%f", timeInterval);
    if (timeInterval < 60) {
       
        NSString *time = @"刚刚";
         NSLog(@"刚刚！！");
    }
    if (timeInterval >= 60 && timeInterval < 3600) {
        int a = timeInterval / 60;
        NSString *time = [NSString stringWithFormat:@"%d分钟前", a];
        NSLog(@"%@", time);
    }
    if (timeInterval >= 3600 && timeInterval < 3600 * 24) {
        int a = timeInterval / 3600;
       
        NSString *time = [NSString stringWithFormat:@"%d小时前", a];
        NSLog(@"%@", time);
    }
    if (timeInterval >= 3600 * 24 && timeInterval < 3600 * 24 * 31) {
        int a = timeInterval / (3600 * 24);
        NSString *time = [NSString stringWithFormat:@"%d天前", a];
       NSLog(@"%@", time);
    }