There is no specific Bonita API that allow you to work on time information. You may use existing java class (such as java.util.Calendar) or use your own custom data type (import it as a jar file in your Bonita BPM Studio). Using groovy is also possible.
Bonitasoft empowers development teams with Bonita, the open-source and extensible platform to solve the most demanding process automation use cases. The Bonita platform accelerates delivery of complex applications with clear separation between capabilities for visual programming and for coding. Bonita integrates with existing solutions, orchestrates heterogeneous systems, and provides deep visibility into processes across the organization.