Easy way to add multi-country holiday calendar to dashboard

Hello Folks,

Please help me with this!

I’m working on a dashboard and planning to add a calendar feature where users can select a country to see that country’s holidays highlighted. Additionally, I want to allow users to select up to three countries simultaneously to compare their holiday dates.
Has anyone implemented a similar feature before, or does anyone have suggestions on the best way to design this for a seamless user experience? Any tips or examples would be greatly appreciated!
Thanks in advance!