gem install 'ruby-caldav'

require 'ruby-caldav'

u = "user1"
uri = "http://yourserver.com:8008/calendars/users/#{u}/calendar/"
cal = CalDAV::Client.new(uri: uri, user: u, password: "password")

result = cal.find_events(start: "2019-04-01", end: "2019-04-15")

result = cal.create_event(start: "2019-04-12 10:00",
  end: "2019-04-12 12:00",
  title: "Some Meeting",
  description: "Meeting about something")