The game ends in 2051; but if you wish you can play on endlessly.
TrueLight:"Did you bother to read any of the replies, or you just pressed 'Reply' and started typing?" <@[R-Dk]FoRbiDDeN> "HELP, this litte arrow thing keeps following my mouse, and I can't make it go away."
what the wonderfully eloquent Darkvator meant to say, was that time in OTTD stops in 2090 and infinitely loops thereafter so you can continue playing, but that the game "ends" in 2051 (when the original ttd ended) (this is the year the score is taken).
The last useful new tech is in 3037 with the lev4 chimaera.
Though the darwin 700 is dated 2043, and as such is the last one to appear.