RTC stands for Real-Time Clock, which is an electronic device that measures the passage of time. It is an integrated circuit that contains a timer that supplies the time of day (and often, the date) . RTCs are present in almost any electronic device which needs to keep accurate time of day, including personal computers, servers, embedded systems, and many other electronic devices. RTCs often have an alternate source of power, so they can continue to keep time while the primary source of power is off or unavailable. This alternate source of power is normally a lithium battery in older systems, but some newer systems use a supercapacitor, because they are rechargeable and can be soldered. RTCs are used in a variety of applications where they play a critical role in keeping accurate track of the current time while also providing alarms, timers, and interrupt functions and helping to reduce power consumption.