There's no time-scale tool.
You can either download a mod that changes this, or manually edit C:\Program Files\SEGA\Medieval II Total War\data\world\maps\campaign\imperial_campaign\descr_strat.txt

There you can set timescale to 1.00 for example, for one turn per year.
Be sure to set it's read-only propertly to false first, though (can be done by right-clicking and selecting properties)