Present

McOS is split up into multiple different times: Present is all of the events after the recreation of the original MaowcraftOS-Terminal server, it includes the following story arcs: The current story arc is the Raine Arc, dominated by the enemies Raine and ctOS 3.0/EnTech Security.
 * Origins
 * Classic
 * Present
 * Orion Arc
 * Paradoxx Arc
 * Raine Arc

The difference between Classic and/or Origins and Present is that Present constantly updates as new events occur, and on the contrary, Classic and Origins build up multiple new plot points as Present goes on.

Trivia

 * There may be undocumented arcs of the story.
 * There is also periods of time where there is no arc.
 * Arcs are usually dictated by the main enemy of the arc.