Cal.com

YES

Replaceable in one session with an AI coding agent.

A booking page: you publish your availability, someone picks a slot, and both calendars get the event. It is the open-source answer to Calendly, and the hosted plan is what you pay for rather than the software.

Promptfree, for everyone, and the only version there is

Build me a booking page for one person.

STACK
- Astro with a Node adapter, SQLite for bookings
- Google Calendar API for reading busy time and writing the event

EVENT TYPES
- Each has a name, a duration, a buffer before and after, and a minimum notice
- A weekly availability grid per type, in my own time zone, stored as that zone and never as UTC offsets

THE BOOKING PAGE
- Show the next 30 days; slots computed from availability minus busy time minus buffers
- Detect the visitor's time zone, show it, and let them change it
- Never show a slot inside the minimum notice window

TIME, AND GETTING IT RIGHT
- Store every instant as UTC and every rule as a named zone
- Test explicitly across a daylight-saving change in both directions — this is the part that breaks

HOLDING A SLOT
- Reserve for five minutes while the form is filled in, then release
- A unique constraint on (event type, start) so two people cannot take the same slot

AFTER THE BOOKING
- Write the event to my calendar with the invitee as an attendee
- Send confirmation email with an .ics attachment and a cancel and reschedule link, each a signed token

Include the schema, the OAuth setup and a README on the daylight-saving tests.

What you lose

Two-way sync with Google, Microsoft and Apple calendars, including the recurrence rules that break naive implementations
Time zones handled correctly across daylight-saving boundaries, which is where most home-made schedulers fail
Video links created automatically on the provider the invitee expects
A hosted instance somebody else patches — the software is free, the operating is what the fee buys

If you would rather not build

Calendly, if you would rather not run anything
A Google Apps Script bound to a form, for very simple cases

The escape hatch

open source · no votes, no paid placement

Cal.com

The product itself, AGPL and self-hostable — the paid plan is the hosting.

calcom/cal.diyfree · open source

Easy!Appointments

A PHP booking system that runs on ordinary shared hosting.

alextselegidis/easyappointmentsfree · open source

Why this verdict

our own opinion · changed only by a person

78/100

Verdict yes at 78 rather than higher: the software is already open source, so "build your own" here really means "self-host theirs", and the fee is for someone operating it. Time zones and recurrence are the honest difficulty.

History

tracked since 10 Aug 2026 · nothing is ever overwritten

Interest · last 30 days

Nothing recorded yet. This chart fills in once the page has visitors, votes or prompt copies — it will not draw a flat line to look busy.

Questions about Cal.com

answered from the record above

Is Cal.com free?

No — the plan we track is $15 a month. Teams at $15 per user per month billed monthly, $12 annually; the individual plan is free.

Can you replace Cal.com by building your own?

YES. Replaceable in one session with an AI coding agent. Replacement score 78 out of 100, build time one session. Read what you lose before you decide.

How much does Cal.com cost?

$15 a month on Teams — $180 a year. Recorded 9 Aug 2026.

What do you lose by replacing Cal.com?

Two-way sync with Google, Microsoft and Apple calendars, including the recurrence rules that break naive implementations; Time zones handled correctly across daylight-saving boundaries, which is where most home-made schedulers fail; Video links created automatically on the provider the invitee expects; A hosted instance somebody else patches — the software is free, the operating is what the fee buys. If any of those carry weight for you, keep paying.

Is there an open-source alternative to Cal.com?

Yes: Cal.com, Easy!Appointments. The prompt on this page is for when you want it your way instead.

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