Explore the theoretical foundations of computational complexity in this enlightening talk from EuroPython 2021. Delve into the concept of time complexity, learning how to formally measure and analyze the execution time of programs and algorithms. Discover the significance of Big-O, Big-θ, and Big-Ω notations in complexity analysis, and examine their practical applications through examples of searching and sorting algorithms. Gain valuable insights into how algorithm design choices impact program execution time, drawing inspiration from the youngest Guinness World Record holder for computer programming.