Microsoft 365 Calendar

Microsoft 365 Calendar Management

Overview

Microsoft 365 calendar is powered by Exchange Online and surfaced through Microsoft Graph. For MSPs, calendar tasks include troubleshooting scheduling issues, creating meetings on behalf of users, managing room resources, and checking user availability during support incidents.

Graph API Patterns

Get a User's Calendar Events

GET /v1.0/users/{userId}/calendar/events?$select=id,subject,start,end,organizer,attendees,isOnlineMeeting,location&$orderby=start/dateTime&$top=10

Get Events in a Date Range

GET /v1.0/users/{userId}/calendarView?startDateTime=2024-01-15T00:00:00Z&endDateTime=2024-01-22T00:00:00Z&$select=subject,start,end,organizer,attendees,isOnlineMeeting

Use calendarView (not /events) for date-range queries — it correctly expands recurring events.

Check Free/Busy Time

Get availability for a set of users:

POST /v1.0/users/{userId}/calendar/getSchedule
Content-Type: application/json

{
  "schedules": ["user1@contoso.com", "user2@contoso.com"],
  "startTime": { "dateTime": "2024-01-20T08:00:00", "timeZone": "Eastern Standard Time" },
  "endTime":   { "dateTime": "2024-01-20T17:00:00", "timeZone": "Eastern Standard Time" },
  "availabilityViewInterval": 30
}

Response:

{
  "value": [
    {
      "scheduleId": "user1@contoso.com",
      "availabilityView": "000022220000",
      "scheduleItems": [
        {
          "status": "busy",
          "start": { "dateTime": "2024-01-20T10:00:00" },
          "end":   { "dateTime": "2024-01-20T11:00:00" }
        }
      ]
    }
  ]
}

availabilityView is a string where each character represents a 30-min slot: 0=free, 1=tentative, 2=busy, 3=out-of-office, 4=working elsewhere.

Create a Meeting (with Teams Link)

POST /v1.0/users/{organizerId}/events
Content-Type: application/json

{
  "subject": "IT Onboarding — Jane Smith",
  "start": { "dateTime": "2024-01-20T10:00:00", "timeZone": "Eastern Standard Time" },
  "end":   { "dateTime": "2024-01-20T11:00:00", "timeZone": "Eastern Standard Time" },
  "attendees": [
    { "emailAddress": { "address": "jsmith@contoso.com" }, "type": "required" },
    { "emailAddress": { "address": "itadmin@contoso.com" }, "type": "required" }
  ],
  "isOnlineMeeting": true,
  "onlineMeetingProvider": "teamsForBusiness",
  "body": { "contentType": "HTML", "content": "<p>IT onboarding session agenda...</p>" }
}

Get Room Resources

GET /v1.0/places/microsoft.graph.room?$select=id,displayName,emailAddress,capacity,building,floorNumber

Check Room Availability

Use getSchedule with the room's email address as a schedule ID (same as users above).

Cancel an Event

POST /v1.0/users/{userId}/events/{eventId}/cancel
Content-Type: application/json

{
  "comment": "Meeting has been rescheduled. New invite to follow."
}

Update an Event

PATCH /v1.0/users/{userId}/events/{eventId}
Content-Type: application/json

{
  "subject": "Updated: IT Onboarding — Jane Smith",
  "start": { "dateTime": "2024-01-21T14:00:00", "timeZone": "Eastern Standard Time" },
  "end":   { "dateTime": "2024-01-21T15:00:00", "timeZone": "Eastern Standard Time" }
}

Common MSP Workflows

Find Available Meeting Time

1. Get list of required attendees
2. Call getSchedule for all attendees + desired room
3. Parse availabilityView strings to find overlapping free slots
4. Return top 3 options within the user's working hours

Out-of-Office and Calendar Coordination

When setting OOO (via mailbox settings), also check if the user has events during their absence:

1. Get events in the OOO date range
2. List events with other attendees — these may need cancellation or reassignment
3. Cancel/update events as needed
4. Set OOO via mailbox settings

Recurring Event Management

Recurring events are expanded in calendarView results. Each instance has:

• seriesMasterId — the master recurring event ID
• type: "occurrence" — individual instance
• type: "seriesMaster" — the template

To update all future instances: PATCH the series master. To update only one instance: PATCH the specific occurrence.

Error Handling

Error	Cause	Resolution
ErrorCalendarNotFound	User has no calendar (no Exchange license)	Assign Exchange license
ErrorItemNotFound	Event ID doesn't exist	May have been deleted
ErrorAccessDenied	No Calendars.Read permission	Check app permissions
Organizer_Invalid	Trying to create event as non-organizer	Use organizer's userId

Permissions Required

Task	Microsoft Graph Permission
Read events	Calendars.Read
Read other users' calendars	Calendars.Read (admin consent)
Create/update/delete events	Calendars.ReadWrite
Check free/busy	Calendars.Read
Room directory	Place.Read.All

Related Skills

• M365 Teams - Teams meetings integration
• M365 Mailboxes - Out-of-office coordination
• M365 Users - Timezone and locale settings