Estimates have been made on many issues in the Jira system. An administrator then deactivates time tracking, reconfigures the time tracking variables of the Jira system from 24 hour days to 7 hour days and reactivates the time tracking. All old estimates are recalculated (correctly) to new huge timescales. An option should exist ("convert original subjective estimates to new timescales" checkbox on time tracking screen) which allows time estimates to be preserved when altering the time tracking variables. For instance, when using the new option, the specification of one day in an issue should remain as one day following the change to the variables.