A real-time clock (RTC) is a computer clock (most often in the
form of an integrated circuit) that keeps track of the current
time. Although the term often refers to the devices in personal
computers, servers and embedded systems, RTCs are present in
almost any electronic device which needs to keep accurate time.
The term is used to avoid confusion with ordinary hardware
clocks which are only signals that govern digital electronics,
and do not count time in human units. RTC should not be confused
with real-time computing, which shares its three-letter acronym,
but does not directly relate to time of day. Although keeping
time can be done without an RTC, using one has benefits: - Low
power consumption  (important when running from alternate power)
- Frees the main system for time-critical tasks - Sometimes more
accurate than other methods A GPS receiver can shorten its
startup time by comparing the current time, according to its
RTC, with the time at which it last had a valid signal. If it
has been less than a