A microcontroller unit (MCU) is disclosed with a stand-alone Real Time Clock (RTC). The MCU includes a processing circuit for receiving digital information and processing said received digital information. A primary clock circuit provides the timing for the processing circuit. A power control circuit controls the power to the processing circuit and the primary clock circuit to control the operation thereof to operate in at least a full power mode drawing a full power level from a supply voltage input and a reduced power mode drawing less than the full power level from the supply voltage input. A stand-alone RTC circuit is also provided, the stand-alone RTC circuit including an RTC clock circuit operating independent of the primary clock circuit. A timer clocked by the RTC clock circuit is operable to increment a stored time value for output therefrom, the RTC clock circuit having a defined time base. An input/output (I/O) device provides access by the processing circuit to the results output by the timer. A power management circuitry manages the power to the stand-alone RTC circuit, such that the RTC clock circuit, the timer, and the I/O device operate regardless of the power mode of operation of the processing circuitry and the primary clock circuit.