Why do I see negative values when I subtract time duration metrics during business hours?

Question

Why do I see negative values when I subtract the native Support time duration metrics, like Full resolution time, during business hours?

Answer

If a ticket schedule changes multiple times, business hours metrics could return negative values. If there is a discrepancy between business hours values, instead use calendar hours values. Calendar hours are not impacted by schedule changes and will remain accurate.

To prevent negative values in business hours metrics, set a schedule early and avoid schedule changes later. If you do see a negative value, check your ticket history to see if the schedule applied to the ticket has changed or if any holidays were backdated in your current schedule.

Note: The schedule at the time of the relevant event may not be the schedule at the time you check the ticket. Use the schedules endpoint to see when a schedule was last updated.

For more explanation on how business hours are recorded, see the article: How does Zendesk record its business hour metrics?