The ultra-bright short-pulsed radiation provided by the free electron lasers (FEL) is used for many new discoveries in different fields of science and industry. The advancement of the FEL technologies allows the generation of shorter photon pulses with higher photon energies or shorter radiation wavelengths that open new horizons for the new research. In order to better understand the measurements using the free electron laser pulses, it is important to know the properties of these pulses. Particularly, for the time-resolved experiments the temporal properties of the photon pulses such as their relative arrival times and the temporal durations, are of utmost importance. One of the techniques to measure these parameters of the FEL pulses is the THz streaking method. Thus far, this method has been used only for the photon pulses in ultraviolet and soft X-ray regions. This thesis provides a full characterization of the method and demonstrates its applicability in the hard X-ray photon energy range, measuring FEL pulses with photon energies of up to 10000 electronvolts. Measurement accuracies of sub-10 femtoseconds were achieved for both the arrival time and the pulse length measurements. Furthermore, it is shown here that the THz streaking method is able to simultaneously measure two FEL pulses of different energies. The results from some measurements were also compared to other independent measurement techniques. In addition to the performed measurements, simulation of the THz streaking effect was performed to better understand the measurement method. The simulations showed the ways of achieving higher accuracies with the THz streaking techniques. The results obtained from the experiments were consistent with the results provided by the simulations. The results obtained in this thesis provide new possibilities for the applications of the THz streaking method. They enable temporal diagnostics for photon pulses with a wide range of wavelengths and temporal durations. Such diagnostics can contribute largely to the success of the experiments performed at free electron laser sources.