CopperEgg will automatically record an alert in your timeline as an annotation. This is an option in any alert.
The corresponding time of the alert will be shaded in a light yellow in your timeline graphs. If you click on the any particular annotation, the corresponding timeline will be highlighted in a darker yellow, as in this screenshot.
This feature will help you better correlate alerts to time frames and easily see events in the past. To enable this feature, be sure the Auto-annotate option is checked for any alert.