Jira Administrator can manage the working calendars Jira Administration → HelpDesk → SLA 2.0 → Calendars.
Creating a Calendar
1. Specify the calendar name and click Add – a new calendar will appear.
2. Select the Edit button to set up the workdays schedule and the Days off, if required.
To get you started, HelpDesk comes with a default 24/7 calendar. You can change it if required.
IN USE Parameter
It's great to know if the entry is being used before changing it. The IN USE parameter displays if there are any SLAs using this calendar (specifically if the calendar is selected in SLAs settings). You should change the calendars in use carefully (it may lead to SLAs recalculating in issues). The calendars in use cannot be deleted.