TL;DR — Google Calendar

Design a calendar scheduling system like Google Calendar that allows users to create events, manage recurring schedules, share calendars, and find mutually available time slots. The system must correctly handle timezone conversions, daylight saving time transitions, and recurring event patterns (daily, weekly, monthly, custom RRULE). Key features: Create, update, delete single and recurring events. Recurring event patterns: daily, weekly, monthly, yearly, custom RRULE.