Thanks to the present Emperor's being born on December 23, we get a day off exactly when we need it.  Right now.  Today.  In the midst of the rush to bring the year to a successful end.
The year-end gift-giving season in Japan is already over.  If you have New Year holiday travel plans, they are already finalized.  So it's not a day to run around on errands.  It's a time out.
Happy Birthday!  And thank you for the present.