Spin is a software package for the verification of concurrent systems. A system to be verified is modeled in Promela — Spin’s input language. We present an extension of Promela and Spin with discrete time that provides an opportunity to model systems whose correct functioning crucially depends on timing parameters. This extension is completely compatible with all the features of the standard package, in particular the partial order reduction algorithm. We have tested the prototype tool on several applications known from the verification literature and the first results are promising.