A Real Time Clock (RTC) is basically just like a watch – it runs on a battery and keeps time for you even when there is a power outage. Using an RTC, you can keep track of long timelines, even if you reprogram your microcontroller or a power plug.The real time clock (RTC) is widely used device that provides accurate time and date for many applications. Many systems such as IBM pc come with RTC chip on mother board.RTC chip uses an internal battery which keeps time and date even when the power is off. In some microcontrollers have inbuilt RTC while others requires interfacing.Most widely used RTC chip is DS1307 from Dallas Semiconductor. It uses external lithium battery of 3V to keep operating for over maximum 10 years in the absence of external power supply.DS1307 uses CMOS technology to keep power consumption low. According to datasheet of DS1307 from Dallas, it keeps track of “Seconds, Minutes, and Hours, Day of week, Date, Month and Year”.