Aslan's Narnia is neither in the past nor the future but exists in a separate fictional universe parallel to our own. Time in Narnia is not necessarily aligned with time in the real world, and the events within the Narnia series take place in their own unique timeline.

The vikings simply fitted in the timeline events - YAWN...

A timeline is helpful because it visually organizes events in chronological order, making it easier to understand the sequence of events and how they relate to each other. It helps in tracking progress, identifying key milestones, and planning future actions based on past events.

Future Gohan cannot transform into super saiyan 2, because the events leading up to (Kid) Gohan's first transformation to said form did not occur in Future Trunks' timeline. Indeed, Cell did not make an appearance in the future timeline because the androids destroyed Earth and its inhabitants.

A timeline shows events in chronological order.