Hi @Jon, 

Welcome to the Community! We are so glad you’re here! Love the idea of sending out a reminder to those who have signed up for online classes. 

Our Help Center has some awesome documentation that will walk you through how to Add Calendar Events in a Button or Link that will sync with your customer’s calendars and add the class or event. You can also  send out scheduled campaigns to go out those who have signed up for each class 24 hours before the classes start, depending on whether or not you’ve grouped them into class-specific lists or segments already. 

However, if you would like to automate this notification through flows, you would need to either integrate with some kind of calendar application that could sync with you customers’ schedules or create a custom event that would trigger the flow. Flows need to be triggered by a specific action to start the automation. A Calendar integration could have an event built into it that you can use to create the flow, however, if you choose to not integrate with an application, you can create a custom event via API. If you follow this route, you will need to contact your dev team or reach out to a Klaviyo partner to create this for you!

Thanks for participating in the Community!

-Taylor