Why January 30 as the release date of the opinion?

Justice Powell wrote to the other Justices that “[i]t is important to make that date if possible. The Act directs us to ‘expedite’ this case. It sounds more ‘expeditious’ for the record to show we brought the case down in January rather than February!”

Quoted in my article, The Untold Drafting History of Buckley v. Valeo.