How to affect timescale (month length) in Dwarf Fortress>

There is no way to change the length of time increments. There are potential ways to get more done in the same time, though this won't change the number of hours per day, days per week, etc.

For example one can make dwarves move extremely quickly. The same page gives information about how to have them learn skills more quickly, and increase their attributes (thus completing some tasks more quickly). It also talks about how to remove their needs for non-work activities. This definitely falls under cheating, but if that works for you then it's nobody else's business.

Another way to make dwarves get more done with their time is to streamline the workflow. This can be done by carefully arranging hauling routes, and by planning item flow around the production stages of the various industries. These are regular fortress optimization tasks.

Sorry there is no way to do exactly what you want, but hopefully this helps some.

There is no explicit way of changing the realtime<->DF time ratio. Increasing FPS, however, does make things happen faster.

You can try one of several methods:

• If you are consistently hitting the FPS cap, unlock FPS by changing [FPS_CAP:100] in data/init/init.txt to [FPS_CAP:0]. In the same section you can disable V Sync and
• Increase FPS by (e.g.) Atom-Smashing unused items from your fortress, use a smaller world/embark, etc. There are more tips on the DF Wiki.
• Get a faster computer. As DF is single threaded, look for a CPU with good single core performance.