For guaranteed delivery by December 25th, the official last date for Parcel Post is usually mid-December. I'm talking about the 12th to the 15th, folks.
Check your specific country’s postal site. Don't trust my memory. I once thought the "buy now" button meant "free shipping." It did not.
If you mail something via Parcel Post after December 14th? You are actively gambling. That package is a hostage situation now.
Parcelforce Worldwide reveals last posting dates Christmas ad - ChannelX
Why Is It So Late?
Volume. The postal system gets crushed like a gingerbread house in a stampede. Every package is fighting for a spot on a truck.
Yours is wearing sweatpants. The Priority packages are in first class. Your Parcel Post box is in the cargo hold, next to someone’s lost luggage from 2019.