Time on Books (TOB) is a dimension used in Lifetime Value and Repurchase reporting. It is meant to indicate how much time has passed from each customer's initial purchase.
Each TOB represents a completed 30-day period. You can think of each TOB as more or less how many months have passed since their initial purchase.
When a customer makes their first purchase, they will show up in TOB 0.
That customer will then be represented in TOB 1 once 31 days have passed from the initial purchase. TOBs will continue to increment like this every 30 days.
So if a customer makes an initial purchase and then a second purchase 100 days later, the first purchase is represented in TOB 0, and it will show that they repurchased in TOB 4.
Incomplete TOB cohorts
Typically in charts that include TOB, the final TOB in the chart will have a lower customer count than all of the others.
This is expected because customers are only added to a TOB once they have completed the 30-day period. Since different customers will have a different TOB starting period, not all of them will have aged into the final TOB yet.
When looking at a TOB chart, unless filtered by a very specific group of customers, remember that the values in each TOB contain information from all customer who have been in that TOB. This means that the number of cohorts in each cohort will be different.
If a TOB has too few customers in it, it can make results unreliable. If results appear strange, click "Explore from Here" to see how many customers are in the TOBs
Because each TOB is 30 days, the results will not exactly match monthly totals.