In some ways the religiosity associated with this misquote is unsurprising when you realise that the actual author was Benjamin Hoff, who wrote "The Tao of Pooh". This book draws on Milne's stories to introduce Taoism to lay Western readers. In addition to accurate accounts of Pooh stories by Milne, it is speckled with dialogue by Pooh and friends that Hoff made up as a narrative device to progress his arguments. In my humble opinion, Hoff's crack at Pooh dialogue is far more in keep with Mine's original tone than other imitators I could mention, but nonetheless this is not a Milne quote as lots of people claim.
Also for the record - even if this cited as a Hoff quote, the wording is still inaccurate. From "The Tao of Pooh", the actual quote goes:
[After an in depth discussion about how to spell "Thursday"]
"Then what is it?" asked Owl.
"It's Today!" squeaked Piglet.
"My favorite day," said Pooh.
But Owl makes this quote more cumbersome for a tattoo (or wall decal or arty chalkboard or whatever), so the poor bird gets written out of the script.