A couple of years ago I posted about the Annunciation falling in Holy Week; and learned a lot from a couple of excellent people on Twitter, as recorded here, including John Donne's excellent poem Upon the Annunciation and Passion Falling upon One Day. 1608.
This year, of course, the Annunciation falls on Good Friday. A wonderful topic for a blog post; and fortunately someone more learned than me has already undertaken that task, and produced a completely fascinating post. If you don't know the Clerk of Oxford's site, now is the time to visit it, and read 'This doubtful day of feast or fast': Good Friday and the Annunciation.