This was everywhere. It's even in my book, The Blank Screen (UK edition, US edition). Comedian Jerry Seinfeld allegedly has a big wallplanner and puts an X through each day that he writes. You can see how it would build up to a chain of Xs and his advice for being as famously productive as he is was this and this alone: “Don't break the chain.”

It is very good advice. He just didn't say it and doesn't do this Seinfeld method.

He was on Reddit's Ask Me Anything discussion this week and when asked about this, said:

“This is hilarious to me, that somehow I am getting credit for making an X on a calendar with the Seinfeld productivity program. It's the dumbest non-idea that was not mine, but somehow I'm getting credit for it.”

Read the whole (very long) discussion directly on Reddit. This point comes about a mile into the chat but there's a lot else to enjoy along the way.