apart from the wait/sleep hy hours

i need to test something to pass by at least 31 days

I take it this is for Deadly Dragons?

I went to Breezehome, entered the console and typed "set timescale to x" where x is something pretty large. If you type "show timescale" it'll show the default (20) so you know what value to set it back to when you're done.

The hours will zip by, just bring up an inventory screen or similar to keep an eye on the game date. Pretty sure this is the only relevant console command.

if you "set timescale to 43200" time runs @ about a month gametime for every realworld minute

whot ever you set it to remember to set it back to 20

Just wondering; can that cause instability in the game or in your savegame?

If you do this inside your house, then you'll be fine (you avoid any strange environmental issues). Your save game won't be affected because you set it back to the default value afterwards.