The time published input port, which appears in multiple protocols, has a slightly different meaning depending on the context.
In most situations, including when previewing a protocol-compliant composition in Vuo, time is the number of seconds since the composition started running.
When exporting a movie, time is the number of seconds from the start of the movie to the beginning of the current frame.
In an exported FxPlug plugin, time is the number of seconds since the start of the clip (for generators and effects) or transition.