There is no way to slow down time however there is a cheat for keeping your sim's needs fulfilled permanently (until you put them back to normal again) so you won't have to worry about the timing what with sleeping and eating and whatever. if you open the cheat bar, ctrl-shift-c, then type in "testingcheatsenabled true", without the speech marks, then shift-click on the household's mailbox, it will give you the options "make all happy" (or something along those lines) which will fulfill all the need bars of everyone in the household, pets included, then shift-click again and choose the option "make needs static" which will keep all the need bars of everyone in the household full until you put the game back to normal again. This will give you all day and night to learn skills, which is faster as the mood is high, and to train pets and whatever else you want to do. When and if you want to put the needs back to normal, shift-click on the mailbox, and choose "make needs dynamic" and this will stop the needs from being fulfilled, they won't all instantly need to be fulfilled, for instance the second you press this option the hunger bar won't empty completely, just all the bars will start to decrease again as normal at a normal pace. Hope this helps!
