Node:Year Cheat, Next:Automatic Track Conversion, Previous:Money Cheat, Up:Sign Cheats (detailed)
Cht: Year <number>
Changes the current year, and this works in both directions. Now you can start your game in the year 2030 with all the Maglevs available, or change it back from 2070 when time stops. The year can be anything from 1921 to 65535 if "eternalgame" is on. Without eternalgame, the years can go only to 2098, although years after 2072 or so won't work correctly because time stops somewhere around then. This cheat really sets the date to December 31st of the previous year, so that the year change can be processed properly. That's also the reason why you can't jump to the year 1920, because the date would have to be set to Dec 31st 1919, which doesn't exist in the game.
Note that when jumping to a year before 1930, you must have "generalfixes" on. Otherwise, the game will lock up when a town tries to build another house.
The cheat also updates the age and service intervals of all vehicles, lest all of your vehicles go to the depot after increasing the year, because they have suddenly aged many years in a few seconds.
It's a good idea to activate the "persistent engines" patch, or you might run out of engines to buy, because their lifetimes are too short by default.