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Holidays management
Whilst being logged as an a Jira's HR group user, from Navigation Bar Menu go to Management (1) ➜ Holiday Schemes (2). To make changes, click on click "Edit" hyperlink (3)
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To remove holiday, simply click its name on calendar and in "Edit holiday" prompt click the "Remove" button.
Workdays
Analogically Access to the Holidays, access to Workdays Workdays schemes, its creation and edition is quite similar:
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Whilst being logged as an a Jira's HR group user, from Navigation Bar Menu go to Management (1) ➜ Workweek Schemes (2). Now you can access workdays scheme's name to view it, or click "Edit" hyperlink directly. Currently viewed/edited workweek scheme is displayed below "Workweek schemes" (3). Whilst being in read only mode, you can quickly swich switch to edition by pressing "Edit scheme" (4) button.
You can choose what days of week will be marked as workdays. Every unticked day will be treated as a bank holiday and thus not taken from user's total e.g. yearly annual leave quota.
After any changes you need to click Update workdays button to apply then to system. By default, every day of week is set as workday except Saturday and Sunday.