Apple has sent out an email stating that like last year, iTunes Connect will be closed down during the Christmas holiday due to employees being given that time off.
Apple is instructing developers to prepare accordingly:
We strongly recommend that you do not schedule pricing changes through the interval pricing system in iTunes Connect that would take effect from December 22 through December 29. Pricing changes scheduled to take effect during this date range will not be reflected in the App Store and the app will become unavailable for purchase.
We also recommend that you do not schedule any apps to go live during the shutdown. Releases scheduled with a sales start date between these dates will not go live until after the shutdown.
And before you ask, yes it is already Christmas time.