I know that with Oblivion and both Fallouts setting the timescale to below 10 (It's 20 by default) could cause issues. I assumed the same of Skyrim though a some have reported setting it to 5 without issue. I always set mine to 10.
You could use a mod so it's a number by default, or you can simply open the console and enter 'Set Timescale to X' where X is the timescale (Again I use 10, so it's half the rate of vanilla Skyrim). The value will be permanent in that specific save like any other save data, meaning if you save after doing it, it will retain that value.
Of course, if you don't save, you'll have to do it again. Changing the value will not affect any other saves. I simply use this command at the start of each game I make once and I'm good to go. Though, like I said a plugin file that does this automatically would be super simple so I'm sure some may exist if you'd prefer using one of those.