I always felt like the "Year of Kahless" likely referred to Kahless's birth or death or maybe some other significant date, like when he unified the Klingon Empire. If that's c. 850 C.E., then you have two points for a slope-intercept equation. Simple algebra!The alternative was to do more math than I really wanted to do for the sake of a dating system that 90% of my readership weren't even going to notice.
Having said that, I apologize to the remaining 10% (which likely includes everyone reading this thread).

Keith, you have to know we care!