Depending on which Time Zone you are in will determine when the game gives you a fresh day.
If you live on the East Coast of the USA, then at 12am (midnight) you can log into the game and you will receive a new list of chores, and you can help one friend.
For me, I'm on the West Coast. So, that means that at 9pm my time, I can log in and get a new list of chores, and help one friend.
Sometimes, I will log in around 7 or 8pm (my time) and do my chores. Then once 9pm rolls around, I can do another set of chores. Some people do that, so they have more to do all at once. But it also means I can't play again until after 9pm the next day. I hope that isn't too confusing.
~Vicks