Explore the critical importance of precision timekeeping in this comprehensive lecture from the National Physical Laboratory. Trace the evolution of timekeeping from historical methods to modern atomic clocks, and understand how Coordinated Universal Time (UTC) is now measured. Learn why accurate timekeeping is crucial for the financial sector, including its role in preventing stock market crashes. Discover time's hidden utility in GPS systems and the risks associated with over-reliance on satellite navigation. Delve into the future of timekeeping, including the development of a nationwide timing infrastructure and next-generation optical atomic clocks. Gain insights into the inner workings of atomic clocks and their extreme accuracy, culminating in discussions about redefining the very concept of a second.