In the AgencyAnalytics platform, you can think of the "All Time" time period option as meaning "All Time for the life of the campaign".
So for example, if you created a specific campaign on January 16th 2017, "All Time" would give you all data from January 16th 2017 through today.
Similarly, if you created another campaign just yesterday, then "All Time" would give you data from yesterday and today.
This was done in an effort to maintain a reasonable load on our servers and - by effect - to keep our prices reasonable. Most customers who select "All Time" don't actually care about data from multiple years ago. So if we were to pull all available data every time the "All Time" period was selected, we'd be needlessly increasing our servers' network utilization for no good reason.
With that being said, all of your data going back to the beginning of time is still available for most integrations! You just need to use the "Custom" time period option when you want to see data going back beyond the date when the campaign was created.