SystemD can be used to run timers in an ad-hoc fashion, much like the at command. Note that jobs added using this timer are NOT persistent across reboots; if the device is rebooted before the timer is scheduled to run it will not run at all.
To run a command at a specified time:
systemd-run --user --on-calendar '2022-10-30 02:30:00' /bin/bash -c 'some command to run'