iOS 时间转换

#pragma mark - 获取当前时间戳
-(NSString *)getTimeSp{
    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];
    //返回13位时间戳－－－－－－12位的去掉 *1000
    NSTimeInterval a=[dat timeIntervalSince1970]*1000;
    NSString *timeString = [NSString stringWithFormat:@"%f", a];//转为字符型
    return timeString;
}

#pragma mark - 获取当前 yyyy-MM-dd HH:mm:ss 格式的时间
-(NSString *)getTime{
    NSDate *fromdate=[NSDate date];
    NSDateFormatter *dateFormat=[[NSDateFormatter alloc]init];
    [dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSString* string=[dateFormat stringFromDate:fromdate];
    return string;
}

#pragma mark - 将yyyy-MM-dd HH:mm:ss 格式的时间转换成时间戳
/**
 *  timeStr : yyyy-MM-dd HH:mm:ss 格式的时间
 */
-(long)changeTimeToTimeSp:(NSString *)timeStr{
    long time;
    NSDateFormatter *format=[[NSDateFormatter alloc] init];
    [format setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *fromdate=[format dateFromString:timeStr];
    time= (long)[fromdate timeIntervalSince1970];
    return time;
}

#pragma mark - 将时间戳转为 yyyy-MM-dd HH:mm:ss 格式的时间
/**
 *  timeStr : 10／13位数时间戳
 */
-(NSString *)changeTimeSpToTime:(NSString *)timeStr{
    unsigned long long createTime ;
    if(timeStr.length == 10){
        // 10位时间戳
        createTime = [timeStr longLongValue];
    }else{
        // 13位时间戳
        createTime = [timeStr longLongValue] / 1000.0;
    }

    NSDate *creatDate = [[NSDate alloc] initWithTimeIntervalSince1970:createTime];
    
    NSDateFormatter *creatDateFormatter = [[NSDateFormatter alloc] init];
    creatDateFormatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    NSString *orderTimeEnd = [creatDateFormatter stringFromDate:creatDate];

    return orderTimeEnd;
}