How do I run ruby code periodically?

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Ruby

AWS

I'm making this project WaterPi: Houseplant Remote Watering and Monitoring System - Hackster.io[^] and need help running this line of code periodically

CLIENT.publish('pump/data', {state:{pump: params['action']}}.to_json)

and in the comments the creator says to just add the right parameters to make it run periodically. I'd like to run it every 2 days but not sure how do that.

What I have tried:

every(2.day, :at => '08:00') do
  CLIENT.publish('pump/data', {state:{pump: params['action']}}.to_json)
  200
end