Chance is correct in that there is no clause in the 9001 Standard requiring dates, only that the organization have a process to assure folks use the correct document. There are a number of methods to assure that.
If you use "version number" then you need a process to assure the available version is the most recent one. Offhand, I can think of at least three separate schemes to accomplish that, none of which involves a date.
If you use "version number" then you need a process to assure the available version is the most recent one. Offhand, I can think of at least three separate schemes to accomplish that, none of which involves a date.