source: https://rationalwiki.org/wiki/Last_ThursdayismLast Thursdayism (alternately Last Tuesdayism! or Last Wednesdayism) is the idea that the universe was created last Thursday, but with the physical appearance of being billions of years old. It's also a counter to the creationism theory. Under Last Thursdayism, books, fossils, light already on the way from distant stars, and literally everything (including your memories of the time before last Thursday) were all formed at the time of creation (last Thursday) in a state such that they appear much older.
Last Thursdayism functions both as philosophical point on how our observations may not match with "reality" and a reductio ad absurdum of the young-Earth creationist idea of omphalism: if the world was created 6000 years ago with the appearance of being made billions of years ago, what is there to stop us from claiming it was made Last Thursday?
This is somewhat of a humor theory or conspiracy in a way but there are people who actually believe this is the case.
I am one of those people who believes certain aspects of time are wrong or off but this is a bit too much for me. Anyone ever hear of it?