for "reboot in 60" the format is not correct.
it should be reboot in <minutes> and not <HH:MM>
labuser@lab01:~$ reboot in 60 Invalid time "60". The valid format is HH:MM labuser@lab01:~$ reboot in Possible completions: <Minutes> Reboot in X minutes labuser@lab01:~$ reboot in 1:00 Reboot is scheduled 2020-11-14 01:00:00