The WTBTS gets its dates by multiplying numbers in the Bible by numbers not in the Bible (such as 7 x 360 = 2520) and then subtracting from them numbers which have no historical significance at all (606 BCE) in order to come up with a number they want to tout as of tremendous importance (1914).
When it's pointed out that there was no Year 0, these experts in Bible chronology change the number that has no historical significance at all to a different number that has no historical significance at all (607 BCE) to arrive at the same number as before (1914).
Then they ridicule everyone else in the world for not acknowledging the invisible significance of the final number (1914) and ignore the fact that for the first 50+ years of their history, they were touting a totally different number (1874) and ridiculing the rest of the world for not acknowledging the invisible significance of that number which they now acknowledge had no significance whatever.
Hope this helps, and stay alive 'til '75!