The short version
Greetings Day is a blog, and the line under the logo, What to write, for every occasion, is the whole editorial brief. New articles go up when they are ready, and everything we have published stays available in the blog archive.
This site grew out of a spreadsheet. Mira Caldwell had been tracking what to write for every occasion for years, mostly to stop repeating the same mistakes, and it turned out other people wanted the same answers.