Hello @GrantH0 ,
That's a great question! This isn't currently a feature within our email editor, but I'd be happy to submit as feedback for you to our developers! In the meantime, as long as your customers have a calendar connected to their email client, if they click on a date typed within your email, most email clients will automatically give them the option to add it to their calendars.
Additionally, we do have our event tool which has a built in "Add to calendar" option. You can read more about using that tool here.
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