时间戳转换日期格式

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出处：http://www.cnblogs.com/libra13179/p/5796082.html

文件下载地址：http://files.cnblogs.com/files/libra13179/sw_wall_clock.zip

/**
 *@brief:         monthLength
 *@details:       Get month length.
 *@param[in]      uint8_t lpyr         1 for leap year, 0 if not.
 *@param[in]      uint8_t month     0 - 11 (january - December).
 *@retval:        number of days in specified month.
 */
uint8_t  monthLength( uint8_t lpyr, uint8_t month)
{

#if 1
    uint8_t days = 31;

    if ( month == 1 ) //February
    {
        days = ( 28 + lpyr );  //2月天数为28  + （是否闰年）
    }
    else
    {
        if ( month > 6 ) // aug-dec    //大于6月的30天的月份为9、11月，此时对应的mon为8、10,--之后变为7、9
        {
            month--;
        }

        if ( month & 1 ) //判断是否为4   6   9  11
        {
            days = 30;
        }
    }

    return ( days );
#else
    const uint8_t month_days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

    if( lpyr )
    {
        goto leap_year_February_days;
    }


    return month_days[ month-1 ];


leap_year_February_days:
    return 29;


#endif
}

解析：上面的代码的对照一下下面的表格

备注其实可以用上面的那个复杂，直接使用空间换时间的方法。

  const uint8_t month_days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

    if( lpyr )
    {
        goto leap_year_February_days;
    }


    return month_days[ month-1 ];


leap_year_February_days:
    return 29;

 下面的代码就不细说了。

/**
 *@brief:          ConvertToUTCTime
 *@details:        Converts UTCTime to UTCTime_struct
 *@param[out]      UTCTime_struct *p_utc_time   pointer to breakdown struct
 *@param[in]       UTCTime_t secTime_param number of seconds since 0 hour, 0 minutes,  0 seconds, on the 1st of January 2000 UTC
 *@retval:         None
 */
void ConvertToUTCTime( UTCTime_struct *p_utc_time, UTCTime_t  secTime_param)
{
    uint32_t day = secTime_param% DAY_LENGTH;
    uint16_t numDays = secTime_param/ DAY_LENGTH;

    /* calculate the time less than a day - hours, minutes, seconds */

    p_utc_time->seconds = day % 60UL;
    p_utc_time->minutes = (day % 3600UL) / 60UL;
    p_utc_time->hour = day / 3600UL;


    /* Fill in the calendar - day, month, year */

    p_utc_time->year = UTC_BASE_YEAR;

    while ( numDays >= YearLength( p_utc_time->year ) )
    {
        numDays -= YearLength( p_utc_time->year );
        p_utc_time->year++;
    }

    p_utc_time->month = 0;

    while ( numDays >= monthLength( IsLeapYear( p_utc_time->year ), p_utc_time->month ))
    {
        numDays -= monthLength( IsLeapYear( p_utc_time->year ), p_utc_time->month );
        p_utc_time->month++;
    }

    p_utc_time->day = numDays;

}

/**
 *@brief:         get_wall_clock_time
 *@details:       general purpose wall-clock timing routine.
 *@retval:        UTCTime_struct
 */
UTCTime_struct * get_wall_clock_time(void)
{
    ConvertToUTCTime(&Global_Time,SecondCountRTC);
    Global_Time.month += 1; //calibration
    Global_Time.day += 1; //calibration

#ifdef RTT_LOG_ENABLED    
    logi(" %d-%d-%d %d:%2d:%2d 
",
         Global_Time.year,
         Global_Time.month,
         Global_Time.day,
         Global_Time.hour,
         Global_Time.minutes,
         Global_Time.seconds);
#endif //RTT_LOG_ENABLED
 
    return &Global_Time;
}


/**@brief Function for handling the WallClockID request timer time-out.
 *
 * @details This function will be called each time the WallClockID request timer expires.
 *
 * @param[in] p_context  Pointer used for passing some arbitrary information (context) from the
 *                       app_start_timer() call to the time-out handler.
 */
static void update_wall_clock_handler(void * p_context)
{
    (void)p_context;
    /* Here we should use RTC attributes */
    SecondCountRTC++;
    
    get_wall_clock_time();
    
}


/**
 *@brief:         wall_clock_init
 *@details:       wall clock initialization
 *@retval:
 */
void wall_clock_init(void)
{
    uint32_t err_code;

    /* set a default value */
    Global_Time.year    = UTC_BASE_YEAR;
    Global_Time.month   = 0;
    Global_Time.day     = 0;
    Global_Time.hour    = 0;
    Global_Time.minutes = 0;
    Global_Time.seconds = 0;

    /* Init ticks from RTC */
    SecondCountRTC = 0;

    err_code = app_timer_create(&WallClockID, APP_TIMER_MODE_REPEATED, update_wall_clock_handler);
    APP_ERROR_CHECK(err_code);

    err_code = app_timer_start(WallClockID, ONE_SECOND_INTERVAL, NULL);
    APP_ERROR_CHECK(err_code);

}

问题来了。

1、请问代码中static UTCTime_t SecondCountRTC能保存多少年？

保存UTC时间对应的秒数变量：UTCTime_t类型即uint32，能保存的年数为2^32/86400/365=136年左右，如果UTC以2000年为起点，则最长可以设置的时间为2136年。

2、请问如果修改起点的年需要修改那些宏定义

#define UTC_BASE_YEAR      2000   //< UTC started at 00:00:00 January 1, 2000

#define UTC_ORIGIN_DAY_OF_WEEK (Saturday) //<2000-01-01 is Saturday