1. Click Profile Icon > Company settings > Resource Setting
2. Click on Date field and select a date
3. Add the holiday description
4. To add more, click on Add More option
5. Once you add or update all your holidays’ list, click on Save

Note: Only Owner and Admin can define the working hour, weekend and holidays list of the company. The Holidays will be removed automatically from your estimated hours while creating a task or allocating a resource.