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Google Calendar ↔ Slack integration

Meetings from Google Calendar show up in Slack on time, and Slack can book, move and answer them

The team plans in Google Calendar and talks in Slack. Without a link people miss a meeting that was moved an hour ago, the channel does not know who is busy, and booking a call means switching to the calendar and back. We connect the two so a channel gets a reminder before each meeting, changes are announced where the team already is, and a meeting can be booked or moved with a short command in Slack.

What moves between the systems

  • Google Calendar → SlackA set time before each event, the channel or the person gets a Slack message with the title, participants and the video link.
  • Google Calendar → SlackWhen an event is moved, cancelled or gets a new guest, Google Calendar tells us at once and the change is posted to the channel, so nobody waits in an empty room.
  • Google Calendar → SlackEach morning the channel gets the day's agenda for the team calendar, one message with all meetings in order.
  • Slack → Google CalendarA short command in Slack books an event in Google Calendar with the guests named in the command, and each guest receives the usual invitation.
  • Slack → Google CalendarButtons under the reminder let the person accept, decline or propose another time without opening the calendar.
  • Slack → Google CalendarAsking in Slack when a group of people is available returns the open slots from their calendars, based on busy and available times only, without exposing what the meetings are.
  • Google Calendar → SlackWhile a person is in a meeting, their Slack status shows it and the end time, and clears itself when the meeting ends.

What we connect

  • We agree which calendars matter: the shared team calendar, personal calendars of certain people, or both, and which Slack channel each one reports to.
  • Each person whose calendar takes part grants access once through the standard Google sign-in; we read events and availability and create events only when asked from Slack.
  • We install a Slack app in your workspace with rights to post in the chosen channels, set statuses and receive commands; it is not added anywhere else.
  • We subscribe to calendar changes so Google notifies us instead of us re-reading calendars, and set the reminder lead time per channel.
  • We agree the wording of the command for booking and the message layout, and choose whether reminders go to a channel, to direct messages or to both.
  • We run a test week with one team: a few meetings, one move, one cancellation and one booking from Slack; then switch on the remaining channels.

Automation scenarios

01

Meeting moved, half the team did not notice

Before the organiser moves the call by an hour, the email notification drowns in the inbox and three people join at the old time.

After the change is posted in the team channel within a minute with the new time and a button to open the event.

02

Finding a slot for five people

Before the manager asks in the channel who is available on Thursday, gets five answers over two hours and books the slot that no longer works for one of them.

After one command returns the shared open slots from the calendars and books the chosen one with invitations to all five.

03

Interrupted during a client call

Before a colleague pings with an urgent question in the middle of a client call because nothing in Slack shows the person is busy.

After the status shows the meeting and its end time, so colleagues wait or ask someone else.

04

The day starts with a scattered agenda

Before the team lead opens three calendars every morning to see what the team has today and posts a summary by hand.

After the day's agenda for the team calendar appears in the channel at the chosen time, in one message.

How it works technically

For those who want to check: each point links to the official documentation page it comes from.

  • Google Calendar can notify an outside program on its own whenever a watched calendar changes — there is no need to keep re-reading the calendar.

    Source: developers.google.com ↗ checked 2026-09-27
  • There is an official query that returns only busy and available periods for a set of calendars — this is what lets an assistant pick a time without seeing the events themselves.

    Source: developers.google.com ↗ checked 2026-09-27
  • Inviting someone to an event puts a copy of that event on their calendar, and the invitee can accept or decline it.

    Source: developers.google.com ↗ checked 2026-09-27
  • A program can request only the entries that changed since its last check, which is how reschedules are picked up without re-reading the whole calendar.

    Source: developers.google.com ↗ checked 2026-09-27
  • Block Kit lets a message carry interactive elements such as buttons and menus; a message can hold up to 50 blocks.

    Source: docs.slack.dev ↗ checked 2026-09-27
  • An app may post about one message per second per channel, whichever way it sends them; short bursts above that are allowed.

    Source: docs.slack.dev ↗ checked 2026-09-27

Limits

The limits come from both systems. Slack lets an app post about one message a second into a channel, so when many meetings start at the same minute the reminders are queued and combined rather than sent one by one. Google limits how many requests a calendar takes per minute, both for the connection and per user, and slows the next minute when exceeded, so bulk changes are grouped and retried with a pause. Buttons and menus in a Slack message are limited to 50 blocks, which is enough for a day's agenda but not for a whole month in one message. Personal calendars take part only after each owner grants access themselves; we cannot read a calendar on someone's behalf.

How to start

Three steps from a first message to work on your project.

  1. 01

    Leave a request

    Describe the task in the form — in text or by voice. Budget and timing are optional.

  2. 02

    We review and estimate

    A developer studies the brief, asks about anything unclear and sends an estimate.

  3. 03

    We start

    Once scope and price are agreed, the work begins.

or write to info@coreviaflow.space

Questions

Slack already has a Google Calendar app. Why a custom link?
If the standard app covers what you need, use it and we will say so. A custom link is for what it does not do: reminders to a shared channel with your own layout, a team-wide daily agenda, booking for a group from one command, rules about which calendars report where, or connecting the same events to your CRM.
Will the app see the contents of private meetings?
Only what you allow. For finding open slots we use the availability view, which shows times but not titles or guests. Full event details are read only from the calendars you choose to report to a channel.
Does a meeting booked from Slack look normal in Google Calendar?
Yes. It is a regular event in the organiser's calendar, each guest receives the standard invitation and can accept or decline it, and a video link is added if your calendar settings do that automatically.
What happens with time zones?
Reminders show the time in the time zone of the person or channel that receives them, taken from their Slack profile, and the event itself keeps the organiser's time zone in Google Calendar.

Tell us what needs to be connected

Describe the task in text or a voice message. We look at your setup and reply with a plan.