[rolling_stone]

for births occuring in 1961

IMO if there is a change in middle of year there should be a notation of such on the page of the change and effective date of the change...

[philman_36]

for births occuring in 1961
Isn't August 14, 1961 and every day after that still part of 1961?
And I would be willing to bet that the manual that came out in January 1961 had "for births occurring in 1961" on it too.

IMO if there is a change in middle of year there should be a notation of such on the page of the change and effective date of the change...
Well if the whole thing was new there wouldn't be any page notices.

Here's a thought...maybe it got changed due to some newfangled equipment being installed!
IBM 1401

That might be an interesting trail to follow.