When exactly is Email Forgiveness Day?

I remember it being April 30th. In fact, I'm sure of it. But, Gimlet Media, the company that produced the podcast where the holiday was invented says Email Forgiveness Day is September 30th. Today.

Gimlet is the first on the search results for the phrase "Email Forgiveness Day." The second is this website that has what appears to be a direct quote from Alex Goldman (one of the inventors of the holiday):

If there’s an email response you’ve wanted to send but been too anxious to send, you can send it on September 30th, without any apologies or explanations for all the time that has lapsed. It doesn’t matter how long it’s been. Just include a link to this explainer, the one you’re reading right now, so that your recipient knows what’s going on. Together, we can all make our inboxes less stressful.

Emphasis their's.

The attribution then links back to the Gimlet page, which doesn't mention Goldman at all.

I am vaguely aware of the Reply All controversy a couple years back. Could that have something to do with it? I don't know enough to have an opinion. But, changing the date seemingly without acknowledging it seems weird . I'll go with thoughtless.

Below the first and second search results are pages of old articles referencing the April 30th date for Email Forgiveness Day.

Which day is it? I need to be forgiven.