How Do Computers Know the Time?

In this article explore how your PC always knows what time it is, and how it is able to remember it even when you turn it off. 

It’s likely that when you first booted up your computer, it already had the time showing correctly. This is because most modern-day operating systems use the Internet to sync with a time server. This lets the computer know what time it is, and your PC sets the clock accordingly.

How does your PC know what time it is ?

The RTC (Real Time Clock) chip remembers the date and time. This timekeeper chip is called CMOS complimentary metal oxide semiconductor chip. The CMOS chip known as CMOS RAM is a memory which also stores the BIOS information of the computer. An it is a volatile memory, that is why it is driven by a low voltage battery having a life of around 5 to 10 years. On desktop computers, the battery looks like a silver colored coin.

How is the computer remembering the time after it shuts down? 

Inside your computer is an internal clock, which keeps track of the time. When your computer shuts down, this clock keeps ticking even if you unplug the PC from the mains. That’s because the computer’s motherboard has a Complementary Metal Oxide Semiconductor (CMOS) battery on it which keeps the clock powered up even if the rest of the motherboard has no power.

Conclusions

Also, on many computers, when you connect your computer to an internet  connection, the OS will go find a time server on the network and query the timeserver for the current time. The OS can use this is to very accurately set your computer's local clock. This uses the Network Time Protocol, also called NTP.