rtcwake

Enter a system sleep state until specified wakeup time relative to your BIOS clock. More information: https://manned.org/rtcwake.

• Show whether an alarm is set or not:
  sudo rtcwake -m show -v
• Suspend to RAM and wakeup after 10 seconds:
  sudo rtcwake -m mem -s {{10}}
• Suspend to disk (higher power saving) and wakeup 15 minutes later:
  sudo rtcwake -m disk --date +{{15}}min
• Freeze the system (more efficient than suspend-to-RAM but version 3.9 or newer of the Linux kernel is required) and wakeup at a given date and time:
  sudo rtcwake -m freeze --date {{YYYYMMDDhhmm}}
• Disable a previously set alarm:
  sudo rtcwake -m disable
• Perform a dry run to wakeup the computer at a given time. (Press Ctrl + C to abort):
  sudo rtcwake -m on --date {{hh:ss}}