Mac Calendar - Complicated Add Event Question

I'm probably not looking at this issue from the right angle, but it's perplexing me. Yeah, it's that big a deal. ;)

I want to add Mardi Gras to my calendar as an event. "Fat Tuesday," is the day before Ash Wednesday, which someone has somehow coded into the US Holidays calendar. Is there a way to add a calendar event based on an event the next day?

For background, Ash Wednesday, Good Friday, Palm Sunday, and Easter (I'm probably forgetting one or two) are based on a special calculation related to the first full moon after the spring equinox. So it's like quantum physics to some people. I might be able to look up when that full moon falls every year, but then I'd have to back track to where Ash Wednesday is, and so on. And if there's a simpler way to do this, I'd like to know.

If it's tied to a later event, add a recurring alert to that event. Alert for 1-day before, with your desired message. It won't show on the calendar, but you'll get the alert. Set it to recur annually.

That’s helpful. Of course I know Mardi Gras is the day before Ash Wednesday, I simply don’t look out for Ash Wednesday, so it sort of sneaks up on me.

And I like Mardi Gras. In two different stints, I was stationed in Biloxi, MS, a reasonable drive to New Orleans, for about 10 years. We even visited New Orleans a few times around Mardi Gras (never ON or even just before). I got used to more build up for Mardi Gras than for a whole lot of other dates, so I’m not happy with it sneaking up on me.

This actually sprang from the realization that Ash Wednesday was ALSO Valentine’s Day this year. So we have Mardi Gras the day before Valentine’s Day, which is weird as all get out.

Update: I found a subscription calendar that includes Mardi Gras here. It has a lot of other dates too, but so do many others. Having this one event was what got my attention.