Real-time clock alarm

It can sometimes be found in the 'Power Management' section of a motherboard's BIOS/UEFI setup.

In Linux, the real time clock alarm can be set or retrieved using /proc/acpi/alarm or /sys/class/rtc/rtc0/wakealarm.

[1] Alternatively the rtcwake utility may be used which prevents problems when using local time instead of UTC by automatically processing the /etc/adjtime file.

systemd can be used to wake a system and run a task at a specific time.

[2] In Microsoft Windows there are different programs which could be used to 'wake up' a computer from standby or hibernation.