Dynamic development in science and technology in the second half of the twentieth century caused, among others, an increase in the interest in methods and techniques for precise measurement of time interval that elapses between two physical events. The main objective of the meters which are used for such purposes is the creation of a numerical representation of the measured time interval with as high accuracy and precision as possible. Since the result of measurement is usually presented in digital form, this operation is called a time-to-digital (T/D) conversion, while measuring devices are universally called time-to-digital converters (TDCs). In this chapter, the most representative methods and techniques used for the measurement of time interval with high resolution and precision are described. This includes time stretching, time-to-amplitude followed by amplitude-to-digital conversion, the counting method, direct time-to-digital conversions with a digital delay line in the single and Vernier versions, as well as single- and two-stage interpolation methods.