RTC_MDAY_SHIFT
| (tm->tm_mday << RTC_MDAY_SHIFT)
tm->tm_mday = ((st_time & RTC_MDAY_MASK) >> RTC_MDAY_SHIFT);
#define RTC_MDAY_MASK (0x1F << RTC_MDAY_SHIFT) /* Day of Month [1-31] */