The Terrible 15 Months?

So I have heard it called the terrible twos and even the terrible threes, but can it really start as early as 15 months? Just recently Elias has figured out walking and now walks all around the house. This means he doesn't want to sit on the potty, he doesn't want his diaper changed, he doesn't want to get his shoes and socks put on, he doesn't want to sit in the stroller...all he wants to do is walk around. And when you do something he doesn't want he squirms, throws toys, screams and cries. If he is on the floor, he even kicks and bangs his fists...a mini tantrum. I thought they were supposed to like doing what their parents wanted at this age? Sigh...I hope this phase doesn't last long.