hwclock [option]

System administration command. Read or set the hardware clock. This command maintains change information in /etc/adjtime, which can be used to adjust the clock based on how much it drifts over time. hwclock replaces the clock command. The single-letter options are included for compatibility with the older command.


You may specify only one of the following options:

-a, --adjust

Adjust the hardware clock based on information in /etc/adjtime and set the system clock to the new time.


Print the kernel’s hardware clock epoch value, then exit.

-r, --show

Print the current time stored in the hardware clock.

-s, --hctosys

Set the system time in accordance with the hardware clock.

--setepoch, --epoch=year

Set the hardware clock’s epoch to year.

--set --date=date

Set the hardware clock to the specified date, a string appropriate for use with the date command.

-v, --version

Print version and exit.

-w, --systohc

Set the hardware clock in accordance with the system time.

The following may be used with the above options:


Print information about what hwclock is doing.


The hardware clock is stored in local time.


Disable /etc/adjtime facilities.


Do not actually change anything. This is good for checking syntax.

-u, --utc

The hardware clock is stored in Universal Coordinated Time.

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