Update
'The launch date for The Witcher has not yet been confirmed,' Netflix said. 'The post was made by Netflix accounts in the Netherlands in error, and not all of the information contained in it is accurate/final.'
The Facebook post having been removed, this is probably a communication error on the part of Netflix. Can we still deduce from this that The Witcher will be released in 97 days? Should we tick off December 17th on our calendar?
We will know more soon. In the meantime, take into account that this is a theory and not official information.