Why does Hubble’s clock have to be reset every 17 years?

NASA will reset the clock on its Hubble Space Telescope after nearly 17 years on Saturday. This is done because Hubble tracks time using a 32-bit elapsed time counter, which counts every 1/8th of a second and can count and store nearly 4.3 billion such intervals. The counter restarts after it hits its final bit, which happens every 17 years.