Apple warns developers that during holidays (December 23 to December 27) there are possible delays in app reviewing times.
There are no App Store submission closures this year though.
Apple Developer: Get your apps ready for the holidays
Tag: Holidays
App Store now accepts app submissions during holidays
Apple made an announcement this year App Store Connect will be accepting app and update submissions during holidays.
This year, we’re pleased to continue accepting submissions in App Store Connect throughout the upcoming holidays. Make sure your apps are up to date and ready for the busiest season on the App Store. Due to anticipated high volume, plan to send time-sensitive submissions early. Please note that reviews may take longer to complete from November 24 to 28 and December 23 to 27.
Apple Developer