Under certain circumstances, data appears for days that are outside the reporting window.
The Adobe Analytics data platform uses a hidden date range referred to as a 'lookback window'. This lookback window is used mainly for attribution purposes. For any given date range, the lookback window uses the full months encompassing the reporting period. For example, if the reporting window date range is September 15 - September 30, the lookback date range would be September 1 - September 30.
If using only hit-based metrics like page views and custom events, the lookback window is not used. However, if using visit-based or reporting window participation metrics, the lookback window heavily affects reports.
Entries and other visit-based metrics
Visit-based metrics, like Entries and Bounce Rate, can attribute data to a day before the reporting window start date range. The most common scenario that this attribution is seen is when visits span midnight. For example:
A user visits your home page at 11:55 PM on September 7.
They visit several pages, the last of which occurred at 12:05 AM September 8.
A week later, you run a daily trended report with the date range September 8 - September 14.
Hit-based metrics like page views would produce expected output; data trended each day from September 8 - September 14. However, visit-based metrics like Entries would also show the above visit on September 7. The visit's attributed entry occurred on September 7, and the lookback window is September 1 - September 31.
Bounce Rate always shows 0% on September 7 in this example. This metric is defined as Bounces/Entries, a hit-based metric divided by a visit-based metric. Bounces consist of a single image request, so they cannot span multiple days. Any Bounces on September 7 occurred outside the reporting window, causing the 0% Bounce Rate for that day.
Other hit-based metrics would also show 0 for September 7 in this report, since those hits are not within the reporting window either.
Consider another similar example:
A user visits your home page at 11:55PM on August 31.
They visit several pages, the last of which occurred at 12:05 AM September 1.
A week later, you run a daily trended report with the date range September 1 - September 7.
In this example, Entries and Bounce Rate would not show data from August 31. The lookback window and reporting window both start on September 1, so data cannot be attributed from August 31.
Reporting Window Participation Calculated Metrics
Reporting Window Participation Calculated Metrics attribute data using the lookback window. When trending these metrics, data is seen back to the start of the month, even if the reporting window start date is later.
Using full months as the reporting date range brings the reporting window and lookback window into alignment. This date range prevents previous data from being attributed to hits outside the reporting window.
The rows with attributed data outside the report date range can be hidden in Analysis Workspace. Ctrl + click the rows you want to keep, right click, then select 'Display only selected rows'.
Adobe is exploring ways to allow the user to have more control over the lookback window.