The Time panel is located at the bottom of the RViz GUI, and it displays the elapsed simulator time. It is most useful when there is a simulator running along with RViz since simulation time always has an offset with the system time. Moreover, we can also reset the initial settings of RViz using this panel.
We can refer to the detailed documentation for developing plugins for RViz at http://docs.ros.org/jade/api/rviz_plugin_tutorials/html/index.html.
This is where the rviz_plugin_tutorials package builds a plugin library for RViz containing two main classes—ImuDisplay and TeleopPanel. Will discuss the ImuDisplay plugin in the following subsection.