> ## Documentation Index
> Fetch the complete documentation index at: https://docs.t3gemstone.org/llms.txt
> Use this file to discover all available pages before exploring further.

# RTC

> Real-Time Clock

Computers use a hardware component called RTC (Real-Time Clock), which is powered by an external battery,
to continue counting the system time during power outages or when the system is turned off and on.

<Note>
  The T3-GEM-O1 board includes an RTC. If you do not use the RTC module, the system time will reset and start
  from 01/01/1970 when you cut and restore power to the board. If the board is connected to the internet,
  the correct time will be set after a while. If you want the time to remain accurate even without internet,
  you must use the RTC.
</Note>

### Steps to Run the RTC

<Steps>
  <Step title="Connect the Battery">
    <Frame caption="Todo: RTC battery connection">
      <img style={{height: "300px", width: "auto"}} className="rounded-lg" noZoom src="https://mintcdn.com/t3gemstone-754bcb96/oFj6OOIrYSQVBj-3/images/under-construction.png?fit=max&auto=format&n=oFj6OOIrYSQVBj-3&q=85&s=272252292237340bb9c15e3cfc27ebc1" width="1038" height="1002" data-path="images/under-construction.png" />
    </Frame>
  </Step>

  <Step title="Send the Current Date and Time Information">
    Next, open a terminal via [serial port](../../../quickstart#2-1-serial-port) or
    [SSH](../../../quickstart#2-3-connecting-via-ssh-over-network). You must send your system time to the
    RTC module once using the following command.

    ```bash theme={"system"}
    gemstone@t3-gem-o1:~$ sudo hwclock -w -u /dev/rtc0
    ```

    If the operation is successful, when you run the `hwclock -r` command, you should see an output similar to the following.

    <CodeGroup>
      ```bash Command theme={"system"}
      gemstone@t3-gem-o1:~$ sudo hwclock -r
      ```

      ```bash Output theme={"system"}
      2025-07-16 08:25:02.160359+03:00
      ```
    </CodeGroup>
  </Step>

  <Step title="Test">
    Turn off your board using the power button on the board or the `poweroff` command, and unplug the power cable.
    After waiting about 10 seconds, power the board back on and run the `date` command. If the displayed date and time
    are correct, the RTC is working properly.
  </Step>
</Steps>