How to Build an App Like Calendly: Features and Cost Breakdown

What It Takes to Build an App Like Calendly

Calendly is a deceptively simple product. A user shares a link. The other person picks a time. Both get a calendar invite. Done. But behind that simplicity is a complex system handling timezone conversions, calendar integrations, availability rules, payment processing, and team scheduling.

If you want to build an app like Calendly, the good news is that the core scheduling flow is well-understood and achievable as an MVP. The bad news is that "simple scheduling" has more edge cases than most founders expect. Timezone bugs alone have derailed more scheduling app projects than any other technical issue.

This guide breaks down Calendly's feature set, explains what you need for an MVP versus what you can add later, covers the hard technical problems, and gives you realistic cost and timeline estimates.

Calendly's Core Feature Breakdown

Before building a competitor, you need to understand what Calendly actually does. Here is a breakdown of every major feature, categorized by importance for your MVP.

What Makes Calendly Work

Your MVP needs six features: scheduling links, event types, availability rules, calendar integration, email confirmations, and timezone detection. That is the minimum set that delivers real value.

Calendar Integration: The Hardest Part

Calendar integration is the feature that makes scheduling apps useful and the feature that causes the most development headaches. You need to connect with Google Calendar and Microsoft Outlook at minimum. Apple Calendar is nice to have but lower priority.

How Calendar Integration Works

Reading availability: Your app checks the user's connected calendar to see when they already have events. It subtracts those times from their availability to prevent double-bookings.

Creating events: When a booking is confirmed, your app creates a calendar event on both the host's and invitee's calendars with meeting details, video conferencing link, and any attached notes.

Two-way sync: If the host reschedules or cancels in your app, the calendar event updates. If the host adds a personal event to their calendar, your app removes that time from availability.

Technical Reality

Google Calendar API is well-documented and relatively straightforward. Microsoft Graph API (for Outlook) is more complex and has inconsistent behavior across different Outlook versions and configurations.

Budget 2-3 weeks for calendar integration, including edge cases:

• Handling OAuth token refresh when tokens expire
• Managing multiple calendars per user (work calendar, personal calendar)
• Dealing with all-day events (do they block availability?)
• Handling recurring events correctly
• Recovering gracefully when APIs are temporarily unavailable

Timezone Handling: Where Scheduling Apps Break

Timezones are the single most underestimated problem in scheduling software. Calendly handles timezones so seamlessly that users do not even think about it. Building that seamlessness requires careful engineering.

The Core Challenge

When a consultant in New York creates an event type available from 9 AM to 5 PM, and a client in London views the scheduling page, they should see times from 2 PM to 10 PM (during EST, UTC-5). During daylight saving time, those offsets change. And they change on different dates in different countries.

What Your App Needs to Handle

• Store all times in UTC. Every timestamp in your database should be in UTC. Convert to local time only when displaying to users.
• Detect the invitee's timezone automatically. Use the browser's Intl API to detect timezone, but let users override it.
• Handle DST transitions. A weekly availability rule that says "available Monday 9-5 EST" shifts to "available Monday 9-5 EDT" when daylight saving time starts. Your app needs to handle this automatically.
• Edge cases around midnight. If availability in one timezone crosses midnight in another timezone, your calendar display needs to handle showing times across two dates.

Recommended Approach

Use a mature timezone library. In JavaScript, the built-in Intl.DateTimeFormat and Temporal API (or the date-fns-tz library as a fallback) handle most timezone operations correctly. Do not try to implement timezone math yourself.

Testing protocol: Test your scheduling flow with users in at least five timezones, including one in the Southern Hemisphere (where DST is reversed) and one that does not observe DST (like Arizona or most of Asia).

Payment Integration for Paid Meetings

Calendly allows users to charge for meetings -- consultants, coaches, and therapists use this heavily. If your scheduling app targets professionals who monetize their time, payment integration is essential.

How Paid Scheduling Works

1. Host creates an event type with a price (e.g., "$150 for a 60-minute consultation")
2. Invitee selects a time and is directed to a payment page
3. Payment is processed before the booking is confirmed
4. If the meeting is canceled within the cancellation policy, the invitee receives a refund

Implementation with Stripe

Stripe Checkout Sessions work well for this:

• Create a checkout session when the invitee selects a time
• Include the temporary hold on the time slot
• On successful payment (via webhook), confirm the booking
• On failed or abandoned payment, release the time slot

Refund policy implementation: Store your cancellation policy (e.g., "full refund if canceled 24+ hours before") and automate refunds through Stripe's API based on the cancellation time.

What Makes Your App Different from Calendly

Calendly is a mature product with hundreds of features. You will not out-feature them. You need a different angle.

Differentiation Strategies That Work

Vertical specialization. Build the best scheduling tool for one specific industry. A scheduling app designed specifically for therapists (with HIPAA compliance, intake forms, and insurance integration) or for fitness instructors (with class-based booking and package pricing) can win against Calendly's general-purpose approach.

Pricing advantage. Calendly charges $10-16/user/month. If you can offer the core feature set at a lower price point or with a more generous free tier, price-sensitive users will switch.

Integration depth. Calendly integrates broadly but shallowly. Deep integration with one ecosystem (e.g., becoming the best scheduling tool for HubSpot users) creates a defensible niche.

Specific workflow automation. Calendly's workflow feature is limited. If your target market needs complex scheduling workflows (multi-step booking processes, conditional logic, approval flows), you can differentiate on automation depth.

Regional focus. Calendly is US-centric. Building a scheduling tool with first-class support for a specific region's payment methods, languages, and calendar customs can capture a market Calendly underserves.

Cost Estimate: Building Your Calendly Alternative

Here is a realistic cost breakdown for an MVP scheduling application.

Ongoing costs after launch: hosting ($20-100/month), email service ($0-50/month), error monitoring ($0-30/month). Total infrastructure under $200/month for the first year.

Use our project calculator for a more detailed estimate based on your specific feature requirements.

Timeline: MVP to Market

Start Building Your Scheduling App

The scheduling market is large and growing. Calendly has proven the demand. Your opportunity is not to copy Calendly -- it is to solve scheduling better for a specific audience that Calendly underserves.

Start with the core scheduling flow. Get calendar integration right. Handle timezones properly. Then differentiate on the features and focus that matter to your target market.

Ready to build your scheduling app? Talk to our team -- we have experience building scheduling products and can help you define your MVP, avoid the common pitfalls, and get to market in 8-12 weeks.