hwclock

Display the current time from the hardware clock

$ sudo hwclock

$ sudo hwclock -w

$ sudo hwclock -s

hwclock [options]

hwclock reads and sets the hardware clock (Real-Time Clock/RTC), which is a battery-backed clock that maintains time when the system is powered off.
The hardware clock can be set to either UTC or local time. Linux systems typically use UTC for the hardware clock and convert to local time for display. Dual-boot systems with Windows may need the hardware clock in local time since Windows expects this.
During boot, the system typically runs hwclock --hctosys to initialize system time from the hardware clock. NTP then corrects for any drift.

-r, --show

Read and display hardware clock time

Set hardware clock from system time

Set system time from hardware clock

Set hardware clock to specified time

Hardware clock is in local time

Hardware clock is in UTC

Adjust for systematic drift

Show debug information

Use specified RTC device (default: /dev/rtc0)

Requires root privileges. Windows and Linux have different expectations for RTC timezone - Linux prefers UTC, Windows prefers localtime. On virtualized systems, the hardware clock may be emulated. Modern systems often use systemd-timesyncd or NTP for time management.

hwclock has been the standard Linux utility for hardware clock management since the early days of Linux. It's part of the util-linux package and replaces older tools like clock.

timedatectl(1), date(1), ntpd(8), chrony(8)