An apparatus includes a host and a memory device connected to the host through a bus. The bus is used to communicate a data clock controlling data write timing during a write operation executed by the memory device and a read clock controlling data read timing during a read operation executed by the memory device. The memory device performs first duty cycle monitoring that monitors a duty cycle of the data clock, generates a first result, and provides a timing-adjusted data clock, performs second duty cycle monitoring that monitors a duty cycle of the read clock, generates a second result, and provides a timing-adjusted read clock, calculates an offset of the read clock based on the timing-adjusted data clock, the result and the second result, and corrects a duty error of the read clock using a read clock offset code derived from the offset of the read clock.