How to set a simple timer

Setup, Configuration and Use Beginners
5

Cron expression is string used to specify schedule,

You can use cron expression in rules, as time-based trigger.

So you put it after when clause in rules syntax

rule "<RULE_NAME>"
when
    <TRIGGER_CONDITION> [or <TRIGGER_CONDITION2> [or ...]]
then
    <SCRIPT_BLOCK>
end

And you can define the needed cron expression manually (after reading about it) or by using this website (https://www.freeformatter.com/cron-expression-generator-quartz.html),