Design Calendar System
Last Updated: December 30, 2025
What is a Calendar System?
A calendar system allows users to schedule, organize, and manage events and appointments across time. It provides features like creating events, setting reminders, handling recurring schedules, and sharing calendars with others.
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The core functionality seems simple: store events with start and end times. However, the complexity emerges when handling recurring events, time zones, conflict detection, and real-time collaboration across multiple users.
Popular Examples: Google Calendar, Microsoft Outlook Calendar, Apple Calendar
This system design problem tests several important skills: complex data modeling for recurring events, time-based queries that span different time zones, conflict detection algorithms, and real-time synchronization across multiple users.
In this chapter, we will explore the high-level design of a calendar system.
Lets start by clarifying the requirements: