The TAO detector is designed to measure the reference spectrum of reactor antineutrinos with high precision for the JUNO experiment. Accurate calibrations together with constant monitoring of the stability of the TAO detector parameters are essential in this case. A multipurpose UV LED calibration system will be used to provide a time uniformity check for all the DAQ channels as well as the set of tests of their conditions including status, SiPM gain, Quantum Efficiency and maximum acceptable rate. Thanks to a controlled two-channel LED generator of nanosecond UV pulses and a special light diffuser, the considered calibration system can imitate real scintillation events like the signal process of inverse beta decay or its background processes. That allows to additionally test the DAQ electronics and the offline analysis pipeline, and study pileup effect. We present the UV LED calibration system design, features, capabilities, results of relevant tests and its implementation in the TAO detector.