 The modern era of formal temporal logic was initiated by the seminal work of Arthur N. Prior, with important precursors such as H. Reichenbach, J. Findlay, J. Łukasiewicz, and J.  Łoś.[1]  From the early 1950s, Prior introduced and analyzed in detail over more than a decade several different versions of Tense Logic, many of which are discussed below. Prior’s invention of Tense Logic was largely driven by philosophical considerations. In particular, the Master Argument of Diodorus Chronus and the intricate relationship between time, (in)determinism, God’s foreknowledge, and human freedom played a pivotal role in his work. Prior was convinced that a proper logical approach could help to clarify and solve such philosophical problems. He introduced temporal operators, studied metric tense logic, was a pioneer in hybrid temporal logic, devised two versions of branching time temporal logic, which he took to reflect the views of Ockham and Peirce, respectively, etc. His work paved the way for the development of the vast and diverse field of temporal logic, with numerous important applications not only in philosophy, but also in computer science, artificial intelligence, and linguistics. For more on Prior’s views and work, see Hasle et al. (2017); Blackburn et al. (2019); and the entry on  Arthur Prior.  A comprehensive overview of the history of temporal reasoning and logics is provided in Øhrstrøm and Hasle (1995). See also Øhrstrøm and Hasle (2006) and Dyke and Bardon (2013, Part I).