Stupid Question...When does the terrible twos end?

My son just turned two and man... I need some hope, advice, or something. I noticed a change in my sons behavior as soon as he turned 18m, but it’s nothing compared to what I’ve been putting up with for the past few days. Random yelling and crying all day, for no reason. I put him in time out and he will cry and yell the entire time. I’ve assessed him and nothing serious seems to be wrong with him. Things that trigger his tantrums are frustration with toys, wanting to climb and sit on my head, basically doing anything he isn’t supposed to do. I’ve been feeling anxious and tense but I’m also trying to stay positive. What are some ways to discipline and control this?