An easy and reliable way is presented to measure the duration of UV femtosecond laser pulses of t < 200 nm. The used autocorrelation techniques are based on two photon absorption (TPA) in different TPA media, especially calcium fuoride (CaF2). For 197 nm the laser pulse energy transmission and the laser induced fuorescence (LIF) of self trapped excitons (STE) at 278 nm are applied. Both methods yield nearly the same second order autocorrelation functions allowing to analyze the investigated laser pulse and obtain its duration of (350 +/ 10) fs.