Hello, Guys
I have a few questions I wanted to ask about Sunday Cancels and a Christmas day cover.
My First question is about the Sunday covers

I've seen a lot of these and wondered how they were canceled on a Sunday. The guy says
"You could ONLY get these large circular day date cancels from the Postal Service Headquarters in Kansas City on these dates."
Is this true and if so could someone explain how the process works.
Also this Christmas Day cover

Does it follow the same thing as the Sunday cover that where is a place that you can get it stamped any day.
I'd just like to know if there fake or if there is a really a way for these to made you know.
Thank you guys for your time and help.