Mean Time to Happen
From Crusaderkings
"Mean Time to Happen" or MTTH, is the average amount of time the game calculates will be necessary for an event to happen.
Unlike most other EU3 games CK uses a slightly more randomized system. How it works is this- every single day there's a small random chance for an event to fire whether it's a cultural or religious conversion or a shiny new level 5 tech. MTTH is the game's estimate of how many years it'll take on average for that event to fire- it does not mean that the event will happen in precisely that exact amount of time.
What this means is that you could theoretically acquire a level 5 tech in a single day or never acquire a level 1 tech throughout the game. While neither is very likely, both are possible. This also means that "progress" in acquiring an event is not saved- you're just as likely to get a level 5 tech 50 years from now as you are that same day. While this may be frustrating in some cases it can also be enjoyable in other cases where events fire much faster than expected- if you're very lucky you may max out siege weapons in under 5 years.
However, don't be dismayed by the system. The trick to handling MTTH is to make sure your PC meets as many bonus conditions for making MTTH fire as possible. For instance, if you meet as many MTTH bonus conditions as possible for cultural conversions then you can make one happen very quickly while meeting none of the conditions leaves you with a base time of 2000 months.
An example of this is increasing Clergy power in your capital province high to improve the MTTH for University research. (further information is in the db folder w/n the game if not presently on the wiki) A high clergy power also makes architecture events fire faster- a clever player will thus research both at the same time to take advantage of the bonuses. Some weapons research also benefits from a high clergy power- a player might also research a weapons tech at the same time that benefits from this.
However, a player may also decide to remain focused on siege tech instead, viewing siege tech as far more valuable, and the bonus as not being worth enough to forego what most players consider to be the most valuable weapon tech.
Alternatively, increasing Clergy power will provide penalties to cultural conversions. Thus it's illogical to try and focus on a cultural conversion in your capital.
For a different example if you're trying to culture-convert capital and disease strikes it then it may make more sense to focus on cultural conversions and less on tech research, as disease significantly increases MTTH (which is a bad thing) while it gives a reduction (which is a bad thing- remember, the lower the MTTH the better!) to cultural conversion.
There are countless bonuses and penalties to the MTTH of the myriad of events which encompass Crusader Kings. Smart players will carefully manage their realms to help speed along MTTH for desired events in each province be it a religious conversion, cultural conversion, tech spread, tech discovery or whatever other goal the PC is pursuing.
Additional explanation of MTTH and it's impact on technology.
