Why does my data change for dates in the past?

Question

Why does my data change for dates in the past? Each time I look at a report for a time period in the past, the data changes. For example, for the period of last month, the query showed a first reply time of 10 hours. A week later, the same query showed a first reply time of 9.7 hours. Why is this?

Answer

There are many reasons why past data may change over time. This is particularly true if the data is sorted by the date a ticket is solved. When an older ticket finally gets solved, replied to, or given a satisfaction rating, that data will show up on past dates in the report.

Data can also change when a solved ticket is re-opened. This impacts things like the number of solved tickets or full resolution time. For example, if a ticket is reopened and resolved during the time you last saw the report, the query will reflect the new time for solving that ticket.