# Prior elapsed time

Elapsed Time Segmentation supports your customer journey analysis and allows you to examine changes in segment membership leading up to a given point - e.g. the datetime that a person made a significant purchase.

Using the [sub-day](<https://help.apteco.com/en/faststats/analysis/segmentation/change-over-time/elapsed-time-points/elapsed-time-sub-day/index.md>) capabilities, you could, for example, report every 4 hours from -24 hours to 0 hours to look at what happened in the time period leading up to the event in question; perhaps a particular marketing campaign provided the appropriate incentive.

Using FastStats selections to define your segments, this type of 'prior' Elapsed Time analysis can also be useful when examining churn. For example:

## What happened in the 48 hours prior to a person choosing to change supplier?

Segments for the preceding time might identify people who have made a complaint...had some kind of bad experience...posted a bad review, etc. As a business you might go on to establish that, of the customers who lapsed, a significant number had some kind of negative experience in the prior days. Having such knowledge allows you to mitigate and develop strategies to retain your customers.

Related topics:

- [Elapsed time points](<https://help.apteco.com/en/faststats/analysis/segmentation/change-over-time/elapsed-time-points/index.md>)
- [Sub-day elapsed time segmentation](<https://help.apteco.com/en/faststats/analysis/segmentation/change-over-time/elapsed-time-points/elapsed-time-sub-day/index.md>)