Nested Events

What are nested events?

Aeon Timeline 2 allows you to nest child events inside parent events so you can break down a task into a number of smaller tasks, or group many related events into a single parent.

When you zoom in, you can choose to expand your parent events to see the individual child events. As you zoom out, expanded parents will automatically collapse, allowing you to see the parent event within the broader context without cluttering your timeline with a lot of unnecessary detail for that zoom level.

Events can be nested many levels deep, allowing you to zoom from a War to a Battle to the timing of events within that battle without affecting your ability to view the overall context when required.

How parent event ranges are calculated

The range of a parent event (i.e. its start and end dates) are calculated entirely from the ranges of its child events, as follows:

The start date for a parent event is equal to the earliest start date of its child events.
The end date for a parent event is equal to the latest end date of its child events.
The duration of a parent event is calculated from the above start and end dates.

Moving parents and all children

To move a parent event and all of its children to a new date, you can drag the parent to a new location in the timeline or change the parent’s start date in the Inspector. When moving a parent event in this way, all of its children (and consequently, grandchildren) will be moved by the same amount to keep the same relative offsets between all affected events.

Adjusting parent without affecting all children

If you wish to extend or contract the range of a parent event without affecting its children, you will need to add, remove or modify individual child events to get the parent range that you want.

Changing an event's parent

You can assign a parent to an event in a number of ways:

When creating the event, select your preferred Parent from the dropdown list. If you choose (No Parent), the event will be created as a top-level event.
Inside the Inspector, modify the Parent field (as pictured above).
Hold down the ⌘ (Mac) or Ctrl (Windows) key and drag your desired child event on top of the intended parent event. You can also hold down ⌘ (Mac) or Ctrl (Windows) and drag an event out of its parent to make it a top-level event.

Preserving newly created parent's ranges

If any of the above actions will add the first child to an event, thus making it a parent for the first time, you will have an additional decision to make.

As described in How parent event ranges are calculated above, a parent event’s dates are entirely decided by their child events. This means that in the normal course of making an event a parent, its existing range (i.e. start and end date) will be lost and replaced by the range of its child events.

If you are building your timeline from the top down (i.e. you have created high level events and are now filling in the detail), this may be undesirable as the parent event may already be carefully positioned (e.g. you have created an event for World War 2 from 1939-1945, and are now wanting to add some key child events within that parent).

Aeon Timeline will prompt you when adding the first child to a parent whether you want to create additional new child events to mark the original start and end of your event:

If you click No, your original parent’s range will be entirely replaced by the range of its new children.
If you click Yes:
- A new event called “Start of XXX” will be added at the original starting location of the parent event.
- If the parent event has a duration greater than zero, an additional “End of XXX” will be added at the original end location of the parent event.
- The children will then be added to the event, and the parent’s range calculated as normal from all of its children.

There is nothing special about these newly created events.

They only represent the original start/end location of the parent and are not tied to the parent event’s start: if you add a child event earlier than the original range, the “start of XXX” event may no longer be at the start of your parent.
You can move them, rename them and delete them just like any other event.

Embed in new parent event

As an alternative to the above, choose Embed in new parent from the Timeline menu or the right-click context menu. This will prompt you to create a new parent event, and then move all of the selected events underneath this newly created event.

This can be useful if you are coming at your timeline the other way and building it from the bottom-up rather than top-down.

Note: when choosing this option, the Parent field in the dialog to create the event specifies the parent of your newly created event (in effect, the grandparent of your selected events).