Calendric and temporal data are omnipresent in countless
Web and Semantic Web applications and Web services. Calendric and
temporal data are probably more than any other data a subject to
interpretation, in almost any case depending on some cultural, legal,
professional, and/or locational context. On the current Web, calendric
and temporal data can hardly be interpreted by computers. This article
contributes to the Semantic Web, an endeavor aiming at enhancing
the current Web with well-defined meaning and to enable computers to
meaningfully process data. The contribution is a reasoner for calendric
and temporal data. This reasoner is part of CaTTS, a type language for
calendar definitions. The reasoner is based on a \theory reasoning" approach
using constraint solving techniques. This reasoner complements
general purpose \axiomatic reasoning" approaches for the Semantic Web
as widely used with ontology languages like OWL or RDF