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the name of a calendar
the number of working days per week
time zone
the number of working hours per day
every day breaks
the days when your team is on holiday.
The time that issue has spent in each status will be calculated according to the specific calendar you choose.
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At the left menu bar of Configuration manager - Work schedules, you can view a list of all the calendars that have been created before. There you You can also create new, copy, copy and delete existing ones.
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Read about how to monitor data about SLA time status at the Report generation SLA Time and Report