How many public holidays calendars can I create?

As many as you need! In Configuration, under the "Public holidays" section, you can create different calendars and assign them to various employees. To do this, click on "+ Add new calendar" (). From there, you can create a new calendar with the public holidays settings you require. Once you've created the new calendar, you'll find a list of all available calendars in the dropdown field. Click on the one you want to use and assign it to the employees.