Make a Calendar Toolkit is an offline Ruby library and command-line tool for calendar grids, US federal holiday dates, business-day arithmetic, recurring pay schedules, rotating shifts, NRF-style retail fiscal calendars, date conversions, SVG and HTML calendars, JSON and CSV data, and date-only iCalendar exports. It is original Ruby code inspired by practical date workflows; it does not call or reproduce the private implementation of Make a Calendar. Created by Ethan, the developer behind Make a Calendar. The project's RubyGems page provides clickable links to the official website and related browser-based date resources.