Badboy -
What edition of the NWT do you have - what is the date of the copyright? The WTS still teaches that Adam was created in 4026 BCE, and used to teach that each creative day was 7,000 years long. Six previous creative days x 7,000 years gives 42,000 years before 4026 BCE, or 46,026 BCE. However the WTS has been reluctant to bring out the 7000-year day idea since 1975, thus my edition question.
As far as 3761 BCE or similar dates - by similar I mean within a couple thousand years - this would be reasonable to anyone who prescribes to the 24-hour "day" in Genesis, including some conservative Christians. You would have to swing a lot of cats to find a Jew who honestly believes this date. Neither six thousand years ago nor 48 thousand years ago corresponds with scientific evident even for the beginning of the Earth, much less the Universe.