Setting dates for Flows or MA throughout the year

I'd like to as if there is any way to do something in Zoho One. Here's the details:

I hold an event several times per year, and know in advance the dates the event will take place. For instance, this year the events will take place July 23, September 24, and December 10. Next year, however, the dates will be different; they may be in the same months (or may not) and definitely on different dates.

The day before each event occurrence, I want to send an email to the people who have registered for that event occurrence. I have the template letter written, and it's going to be the same email each time.

What I want to do is set "something" where at the beginning of the year, once I know the dates, I can put them, and have the system check to see if it's the day before, then send the email.

I was thinking of possibly using Sheets where each event occurrence is in a separate row. Once the event is finished, it either marks the event as "complete" in Column B, or simply deletes the row.

I hope that's clear.

I could do something in Flow, but I'm not sure what it would look like. Can anyone provide some examples?

What I'm doing now is going into the flow I have created, and editing the custom function which makes that date available to the flow. What I'd trying to do, in short, is avoid editing that function every time with the new date.