The events settings is "Event Calendars" on Coyomi iPhone app.
You can set multiple event calendars.
The day if the events exists, ● is shown below the day.
The calendar you use must be registered with Apple's "Calendar" app.
The holiday settings is "Holiday Calendar" on Coyomi iPhone app.
Holidays are displayed in a different color from the normal day. (Color varies with theme)
iPhone has a calendar of holidays installed by default.
In the case of the United States, it will be a calendar named "US Holidays".
We recommend setting that calendar.
The default holiday calendar depends on the iPhone's regional settings.
Regional settings is in iPhone's Settings > General > Language & Region > Region.
If you do not see the correct holiday calendar,
there is a chance to fix it once you set the regional settings again.
Please set the region to another value and then set the correct region again.
If you want to customize holidays, please create your own calendar.