Resolved! Bug in LL_RTC_ALMB_SetDay() in stm32l1xx_ll_rtc.h
In stm32l1xx_ll_rtc.h, generated by STM32Cube MCU Package for STM32L1 Series, v1.8.1, line 2110:__STATIC_INLINE void LL_RTC_ALMB_SetDay(RTC_TypeDef *RTCx, uint32_t Day) { MODIFY_REG(RTC->ALRMBR, (RTC_ALRMBR_DT | RTC_ALRMBR_DU), (((Day ...