If I completely shut down a computer and not use it for months, how can it still tell the time accurately? (given that it isn’t immediately connected to the internet)



If I completely shut down a computer and not use it for months, how can it still tell the time accurately? (given that it isn’t immediately connected to the internet)

In: Technology

Most if no all computers have a battery backup for stuff like that. If you turn your computer on and the date and time is wrong that battery is dead.

A computer’s motherboard has a battery, known as the CMOS battery. This battery remembers all the basic BIOS settings on a computer and keeps track of the time and date. If you remove this battery and leave it off for a while you’ll notice all BIOS settings have reset and your time will also have to be re-synced.

You are not shutting it down completely. CP has a battery on the motherboard that is there to power the real-time clock and to keep bios setting.

For a desktop, it is often a button cell battery that is easy to switch but in a laptop, it is often soldered on.

Just looked at a motherboard like [one of ASUS’s current models](https://www.asus.com/se/Motherboards-Components/Motherboards/ProArt/ProArt-B550-CREATOR/) and the battery is trivial to spot. It is the large silver-colored circular you seed in just to below the initial P in “ProArt B550-CREATOR” that is printed on the motherboard.

Inside the computer there is a battery on the motherboard.

It provides the power to the current settings of a program called BIOS.

BIOS is a simple program that has a handful of settings that in the end, tell the hardware in a computer to start up everything and load Windows (or other operating system).

They’re never truly off. CMOS battery. It keeps the board alive with a tiny amount of current to store settings and keep time. If you’re going to store a machine for more than a year, pull the battery. Sometimes they corrode.

Ahhhh loling… anyone remember the Apple LCII?

Apple shipped it with a horrific CMOS battery/MB combo that would fail within a month or two of not being powered on. This system was marketed to Education where… surprise… no on would turn the damn thing on for a few months at a time.

It would not boot showing bad disk error.

Pop a new CMOS battery in, reboot and reset date and time…

Apple has only gotten worse since but $15 for the battery and another $40 labor for the few torx screws was a bargain back then.

There’s a watch battery (usually a CR2032) on the mainboard of almost all modern computers that keeps the clock circuit ticking over, just like in your digital watch (which uses the same kind of battery and can go years, especially if it doesn’t have to display the time at all). Even things like satellite TV boxes have them in, for the same reason. They didn’t use to, but for decades now the chips are standard and there’s likely a CR2032 sitting (maybe upright) in that box keeping the time.

To be honest, the only mass-market device I know that doesn’t have an RTC is the Raspberry Pi / Arduino, and both have “hats” you can buy to add one on. Those hats use… a CR2032 battery and the same chip as everyone else.

But in the modern day, it barely matters because you don’t need an accurate time for most things, the thing you really need an accurate time for is things like checking secure certificates on websites, and by the time you’re there, you’re already online and likely picked up an incredibly accurate time from an NTP server on the Internet (usually time.windows.com or pool.ntp.org).

The only thing I know that demands a correct time, albeit quite inaccurate, is logging onto a Windows domain computer (where the time has to be within about 5 minutes of the server). But, again, one of the first things that computer will do is talk to the domain controllers and try to pick up a time from them.

There is an internal battery that allows the processor to tell time efficiently, so even if you shut it down and disconnect the power cable it will still be able to tell time, just like a watch has a battery that lasts months and even years.

There’s a tiny battery operated clock on the motherboard. It keeps time when the computer’s switched off.

If you look inside your computer somewhere on the motherboard (the big main circuit board, can’t miss it) there’s a round little battery. The main purpose is to ensure that bios settings and the time and date are kept up to date. Eventually of course the battery will die and at this point when you power the computer on the date and time will reset to the default time.

There is usually a small “coin” battery on the main board, which powers the computer just enough to keep the date and time. If it were to run out, or you were to take it out, then it would not keep the time.

Not all computers do this.

I’ve tinkered with a Raspberry Pi 3, and it absolutely always needed to stay powered on or use an Internet service to know the time.

The difference between computers that can keep the time and ones that can’t is a “realtime clock” (RTC) circuit or chip.

An RTC is typically powered by a little coin cell battery. On a PC, this battery is usually also used to retain some of the computer’s basic hardware settings in its BIOS or UEFI.

Most if not all computers have a 2032 battery on the motherboard that supplies power to keep time and date accurate.

CMOS battery on the motherboard that keeps the data on your BIOS chipset from losing power and resetting to factory defaults. Also there is a time keeping circuit that has a crystal inside it that is designed to oscillate at a specific frequency when specific voltage is applied to it. That is also how the CPU keep its timing as well. Without that crystal oscillator your whole system would be out of whack and nothing would work properly.

There is a small button battery called a CMOS battery. They last for years but not forever. Your average consumer computer is replaced before the battery needs to be. But the do go bad and if the pc off and unplugged it will lose it’s time.

If you have a computer that you turn off and don’t use for months sell it and stick to the comforts of the analog contraptions that your boomer ass has been acustomed to.

The motherboard has a small battery about the size of a quarter called a CMOS battery, it’s responsible for keeping time. The MOBO keeps time, and other BIOS/UEFI settings. If the little battery fails, your computer will stop keeping track of those things accurately.

There’s a small coin sized battery stuck onto the motherboard that powers a clock that keeps track of time.

There is something called a CMOS battery inside the computer on the motherboard. Its basically a very small car remote type battery, you know the flattened CR2032 like ones. Like flattened watch batteries. Anyhow, this battery keeps a timer awake. And it draws very less power to do that. Once this battery is dead, your computer wont be able to tell the time. This battery stays functional even when you switch off your computer.

So, a desktop PC has that little battery. What about my phone? If my phone dies and I don’t charge it for 15 hours, how is the time correct when I finally do charge it and fire it up? Same idea? There’s also a little battery in there too?