The PeriodO gazetteer is a collection of period definitions with coordinates in both time and space, drawn from authoritative sources and provided as structured data with globally unique, persistent identifiers. This growing collection of period definitions seeks to provide a common reference for descriptions of named time-spans in the past (like “the Archaic period” or “the Iron Age”), in the same way that Pleiades provides a common reference for places in the past. Because PeriodO definitions can be located in both time and space, and because the gazetteer records an unlimited range of definitions for the same period term (and different terms for the same chronological span), PeriodO URIs can be used to connect periodized data across databases that use different chronological definitions or terminology. This workshop will introduce participants to the project and demonstrate the searching, browsing, and visualization tools in the PeriodO web interface. It will also provide hands-on demonstrations that explain how users can submit their own preferred period definitions and how PeriodO URIs can be easily added to period terms in a user spreadsheet through Open Refine. Participants are encouraged to bring their own research-specific period definitions and/or periodized datasets.