Planck time is the smallest measurable unit of time in the universe, defined as approximately 5.39 \times 10^-44 seconds. It is derived from fundamental constants, including the speed of light, Planck's constant, and Newton's gravitational constant. This tiny duration represents the time it takes for light to travel a distance equal to the Planck length. In the realm of physics, Planck time is significant because it sets a limit on our understanding of the universe's earliest moments, such as during the Big Bang. At this scale, the effects of quantum mechanics and gravity become intertwined, challenging our current theories of physics.