you need to go to the clock screen.
go to the icon that shows the happiness and hunger meter and keep on pressing a until you see three options appear on your screen. press b and then you have to pick the first option i think.
this is the clock set-up screen and it will freeze the time.
so let's say you're out of your house for groceries or something, and you pause it at 12:30 pm, when you come back it will still say 12:30 pm. so you'll have to change the time when you want to "unpause" it
hope this helps c: