Sometimes we need to have a list of all public holidays. For example if we need to calculate working days. Instead of manually entering all the holidays, you can use Google Calendar.
You can add a Calendar under Regional Holidays and then import this calendar as a Data Source to your App.
Some regions have special holidays, so you can import the ics file for that region to your Google Calendar.
Example for Germany: https://www.ferienwiki.de/exports/de