The ‘Days since last visit’ dimension measures the amount of time passed between the current hit of the visitor and their previous visit (if there is one). This dimension helps you understand behavior visitors make after visiting your site. Examples include:
First-time visitors are not included in this dimension.
This dimension works out of the box for all implementations. If a report suite contains data, this dimension works.
Dimension items include the number of days between a visitor’s last visit and the current hit. Each number of days is a separate dimension item, with
"Same day" occurring where a visitor’s last visit and the current hit happened on the same day.