EPCalendarPicker is an open source calendar Swift based calendar component submitted by Praba.
EPCalendarPicker supports a wide variety of color customizations allowing you to provide different areas of the calendar chart.
Delegates are provided allowing you to return selected dates, you can specify a range of dates for users to scroll through and presents users with the option to scroll to the current date.
Here is an animation from the readme showing a calendar created with EPCalendarPicker:
You can find EPCalendarPicker on Github here.
A nice Swift component for creating customizable selectable calendar views.