$ Linux Command

System

clock

Read or set the hardware clock on older systems.

timehardware clockrtcsystem

Additional Notes

clock is an older command for reading or setting the hardware clock, also called the real-time clock or RTC. On many Linux systems, hwclock is the modern/common command.

Use this page mainly for legacy command recognition.

Syntax

clock [options]

Parameters

  • options: Read, set, UTC/localtime, and system-clock synchronization controls depending on implementation.

Common Options

  • -r: Read the hardware clock on some implementations.
  • -w: Write system time to the hardware clock on some implementations.
  • -s: Set system time from the hardware clock on some implementations.
  • --utc: Treat hardware clock as UTC when supported.
  • --localtime: Treat hardware clock as local time when supported.

Examples

clock -r

Read the hardware clock on systems that provide this command.

hwclock --show

Common modern equivalent.

timedatectl

Inspect system time configuration on systemd systems.

Practical Notes

  • Prefer hwclock or timedatectl on modern Linux.
  • Incorrect hardware-clock settings can cause boot-time and certificate problems.
  • Be careful with UTC versus localtime settings, especially on dual-boot systems.