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Google Calendar to Outlook Calendar Sync

Bidirectional sync between Google Calendar and Outlook to ensure events are visible across both platforms.

Google CalendarOffice 365 Outlook

Unique name

flowLibsGoogleCalendarOutlookSync

Publisher

FlowLibs (flowlibs)

Version

1.0.0.3

Components

5 env vars + 1 cloud flow

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What it does

Overview

A bidirectional, scheduled sync that mirrors events between a user's Google Calendar and Outlook calendar. Every 15 minutes the flow inspects both calendars across a configurable look-ahead window, identifies events present on one side but not the other, and creates the missing copy on the opposite side. Synced events are tagged with a configurable prefix (default [Synced]) so the flow can deterministically skip events it produced itself, preventing infinite re-sync loops.

Why you'd use it

Use Case

Knowledge workers who run separate personal (Google) and corporate (Microsoft 365) calendars routinely miss meetings because the two views don't agree. Manual cross-posting is error-prone. This flow keeps a unified, time-bounded picture without requiring users to give up either calendar — making it a strong fit for IT Admins enabling BYO-Google scenarios and any business user with a split calendar lifestyle.

Step-by-step

Flow Architecture

Run Every 15 Minutes

Recurrence

Scheduled trigger that fires every 15 minutes (frequency: Minute, interval: 15).

Initialize varGoogleCalendarId

Initialize variable

Init a string variable from the flowlibs_GoogleCalendarId env var (default `primary`).

Initialize varOutlookCalendarId

Initialize variable

Init a string variable from flowlibs_OutlookCalendarId (default `Calendar`). This is the Outlook calendar `table` path parameter.

Initialize varSyncWindowHours

Initialize variable

Init from flowlibs_SyncWindowHours (default `24`). Controls how far ahead of `utcNow()` to consider events.

Initialize varSyncTagPrefix

Initialize variable

Init from flowlibs_SyncTagPrefix (default `[Synced]`). Used to mark synced events on both sides so they aren't re-mirrored.

Initialize varTimeZone

Initialize variable

Init from flowlibs_TimeZone (default `Eastern Standard Time`). Windows time zone identifier for Outlook event creation.

Compose Sync Window Start

Compose

Composes `utcNow()` as the start of the look-ahead window.

Compose Sync Window End

Compose

Composes `addHours(utcNow(), int(variables('varSyncWindowHours')))` as the end of the look-ahead window.

List Google Calendar Events

Google Calendar — ListEvents

Calls `shared_googlecalendar / ListEvents` with `calendarId`, `timeMin`, and `timeMax` set from the two Compose steps.

Solution config

Environment Variables

Schema name	Type	Default	Description
flowlibs_GoogleCalendarId	String	primary	Path parameter for the Google Calendar `ListEvents` / `CreateEvent` calls. `primary` selects the signed-in user's main calendar.
flowlibs_OutlookCalendarId	String	Calendar	Path `table` parameter for Outlook `V4CalendarGetItems` / `V4CalendarPostItem`. `Calendar` selects the user's default calendar.
flowlibs_SyncWindowHours	String	24	Number of hours ahead of `utcNow()` to mirror. Larger values mean slower runs and more API quota use.
flowlibs_SyncTagPrefix	String	[Synced]	Prefix applied to mirrored event titles. Required to avoid infinite re-sync.
flowlibs_TimeZone	String	Eastern Standard Time	Windows time zone passed to `item/timeZone` when creating Outlook events. Must be a valid Windows TZ identifier.

Auth dependencies

Connectors & Connections

Connector	API name	Actions used
Google Calendar	shared_googlecalendar	ListEvents CreateEvent
Office 365 Outlook	shared_office365	V4CalendarGetItems V4CalendarPostItem

Note — All connections are referenced as solution connection references; the flow is portable between environments as long as a connection is mapped at import time.

Tweaks & variations

Customization Guide

Almost every realistic variant of this flow can be implemented by changing environment variable values. A few cases require small edits inside the flow definition — those are called out explicitly below.

Change which calendars sync: Update flowlibs_GoogleCalendarId to a non-primary calendar's ID, or flowlibs_OutlookCalendarId to a shared mailbox's calendar name. Both env vars are simple strings — no flow edits required.
Adjust the look-ahead window: Set flowlibs_SyncWindowHours to 48, 72, etc. Keep this proportional to how frequently events are added to either calendar.
Adopt a different sync marker: Change flowlibs_SyncTagPrefix to e.g. >> or [GCAL]. Existing mirrored events will need to be renamed manually or they will be re-synced on the next run.
Alter the schedule: Edit the trigger's Recurrence (15 Minute default) — frequencies under 5 minutes risk Google Calendar quota throttling.
One-way sync only: Delete the corresponding For Each block (the Google→Outlook or Outlook→Google loop) to disable a sync direction.
Run as a service account: Re-author each connector reference using a service account so meeting room calendars or shared mailboxes can be mirrored.

Helpers & literals

Key Expressions

The flow is intentionally light on Power Fx / WDL gymnastics — the heaviest expressions are the branch-name concatenation and the approval outcome check. They are listed below in the order they appear in the flow.

EXPR.01Sync window end

Computes the upper bound of the look-ahead window from the configurable hours env var.

workflow definition language

addHours(utcNow(), int(variables('varSyncWindowHours')))

EXPR.02Outlook OData filter

Builds the `$filter` string passed to `V4CalendarGetItems` so Outlook only returns events inside the sync window.

workflow definition language

concat('Start ge ''', outputs('Compose_Sync_Window_Start'), ''' and Start le ''', outputs('Compose_Sync_Window_End'), '''')

EXPR.03Skip already-synced Google events

Filter-array predicate used to drop Google events that this flow already mirrored from Outlook.

workflow definition language

not(startsWith(coalesce(item()?['summary'], ''), variables('varSyncTagPrefix')))

EXPR.04Mirrored title (Google → Outlook)

Prepends the sync tag prefix to the source Google summary when creating the Outlook event.

workflow definition language

concat(variables('varSyncTagPrefix'), ' ', coalesce(items('For_Each_Google_Event_To_Sync_To_Outlook')?['summary'], '(No Title)'))

EXPR.05Outlook event start (date-no-tz format)

Formats the Google event start so it matches the no-offset format Outlook expects on `item/start`.

workflow definition language

formatDateTime(items('For_Each_Google_Event_To_Sync_To_Outlook')?['start']?['dateTime'], 'yyyy-MM-ddTHH:mm:ss')

EXPR.06Match-existence test

Condition expression — true when no existing mirrored event was found, meaning we should create one.

workflow definition language

equals(length(body('Filter_Outlook_For_Existing_Match')), 0)

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Google Calendar to Outlook Calendar Sync

Overview

Use Case

Flow Architecture

Run Every 15 Minutes

Initialize varGoogleCalendarId

Initialize varOutlookCalendarId

Initialize varSyncWindowHours

Initialize varSyncTagPrefix

Initialize varTimeZone

Compose Sync Window Start

Compose Sync Window End

List Google Calendar Events

Environment Variables

Connectors & Connections

Customization Guide

Key Expressions

EXPR.01Sync window end

EXPR.02Outlook OData filter

EXPR.03Skip already-synced Google events

EXPR.04Mirrored title (Google → Outlook)

EXPR.05Outlook event start (date-no-tz format)

EXPR.06Match-existence test

Customize & download

List Outlook Calendar Events

Filter Google Events Not From Outlook

Filter Outlook Events Not From Google

For Each Google Event To Sync To Outlook

For Each Outlook Event To Sync To Google

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